Gadolinium Salts and Its Chelates -Clinical-experimental Studies

Basic Experimental Studies and Clinical Aspectsof Gadolinium Salts and Chelates

L. Christofer Adding,1 Gerard L. Bannenberg,1 Lars E. Gustafsson1,2

1Department of Physiology and Pharmacology, and 2Institute of Environmental Medicine,

Karolinska Institute, Stockholm, Sweden.

Key Words: Gadolinium chloride — Macrophage — Nuclear magnetic reso-nance imaging — Stretch — Stretch-activated ion channels

ABSTRACT

Gadolinium is a lanthanide that has in recent years become more commonly present inour society. Organic chelates of gadolinium are increasingly used as contrast agents for theimaging of body fluids. Although adverse reactions to these agents are uncommon, it isknown that gadolinium salts can bring about a wide variety of changes in physiology.Gadolinium chloride is widely used experimentally as an inhibitor of stretch-activated ionchannels and physiological responses of tissues to mechanical stimulation. It is also em-ployed as a selective inhibitor of macrophages in vivo. In this review, the known bio-chemical actions of gadolinium are brought together with its in vivo pharmacology andtoxicology.

INTRODUCTION

The cardiovascular and respiratory systems are subjected to a continuous cyclic stretch(rhythm of the heart beats and ventilatory movements) that may be an important stimulusin regulating physiological and pathophysiological processes in these systems. Variouscardiovascular and pulmonary reflexes are mediated by specialized stretch-activatedmechanosensors such as the baroreceptor neurons of the great arteries and the slowly orrapidly adapting stretch receptors of the lung. Recently it has been discovered that me-chanical stimulation can also influence the physiology of other cell types, e.g., endothelialcells and cardiac myocytes. In our view, any mechanical deformation of normal cell shapewill “stretch” the cell. Thus, types of stretch can range from pressure, which can be pos-itive (increased perfusion of a vessel) or negative (hypotonic cell swelling), flow over acell surface (e.g., shear forces to an endothelial cell), elongation of cells (muscle cells),

41

Cardiovascular Drug ReviewsVol. 19, No. 1, pp. 41–56© 2001 Neva Press, Branford, Connecticut

Address correspondence and reprint requests to: L. C. Adding, Div. of Physiology, Dept. of Physiology andPharmacology, Karolinska Institute, S-17177 Stockholm, Sweden.Phone: +46 (8) 728-7214 �7226; Fax: +46 (8) 33-20-47; E-mail: [email protected]

mailto:[email protected]

bending (bone tissue). Stretch can lead to intracellular biochemical changes in a processcalled mechanotransduction. The existence of several stretch-activated (mechanogated)membrane ion channels has been revealed which modulate intracellular ion concentrationsin response to stretch and thereby control cellular function. The most commonly used drugto study the role of such stretch-activated membrane ion channels has been gadoliniumchloride (GdCl3), a lanthanide which has some biophysical properties that are similar tothose of calcium. A limited number of stretch-related functional studies using whole organpreparations and GdCl3 have been performed revealing the importance of stretch-activatedchannels in physiological and pathophysiological conditions. The in vivo pharmacology ofGdCl3 is also beginning to be better understood. The clinical use of gadolinium-containingcompounds is limited to organic chelates of gadolinium, which are used in nuclear mag-netic resonance (NMR) imaging. Such gadolinium-based contrast agents usually show nobiological activity, but toxicological studies have nevertheless been performed to under-stand the potential deleterious effects of gadolinium salts on the body. This review sum-marizes the pharmacology and toxicology of gadolinium with special reference to theproperties of gadolinium as an inhibitor of stretch-activated channels and a blocker ofmacrophage function.

PHYSICAL AND CHEMICAL PROPERTIES OF GADOLINIUM

Gadolinium, atomic number 64, belongs to the lanthanide series; a group of fifteen ele-ments (atomic numbers from 57 to 71) named after lanthanum, the first member of theseries. These elements were earlier called the rare earth elements because their oxides areuncommon compared to the more familiar metallic elements. Gadolinium has a standardatomic weight of 157.25. Gadolinium is silvery white, has a metallic luster, and isformable. At room temperature, gadolinium crystallizes in the hexagonal, close-packedalpha form. The trivalent gadolinium ion (Gd3+) is chemically very close to the divalentcalcium ion (Ca2+) as reflected in size (radius of Gd3+ 1.05–1.11 Å and Ca2+ 1.00–1.06 Å),bonding, coordination and donor atom preference (31). Gadolinium has unusual super-conductive properties, is used in microwave applications and gadolinium compounds areused for making phosphors in color television sets. Furthermore, gadolinium exhibitsferromagnetic properties and solutions of gadolinium compounds are used as intravenouscontrasts to enhance images of patients undergoing NMR.

CLINICAL USE OF GADOLINIUM

Nuclear magnetic resonance imaging of different organs has had a major impact on thediagnosis of a variety of diseases. Chelates of gadolinium are used to provide enhancedcontrast between healthy and diseased tissue, for recent reviews see (88,95,104). Of allelements, the gadolinium ion has the strongest effect on the T1 relaxation times owing toits 7 unpaired electrons (118). Non-complexed gadolinium ion is unsuitable for clinicaluse because it may precipitate and is retained for long periods in the body. Using gadolini-um in the form of stable chelates largely eliminates the insolubility and toxicity of gadoli-nium. Mostly used for this purpose are derivatives of EDTA (ethylene diaminotetraaceticacid). The dimeglumine salt of the gadolinium complex of diethylene triaminepentaaceticacid (Gd-DTPA, Magnevistâ) is widely used clinically (119). A good understanding of the

Cardiovascular Drug Reviews, Vol. 19, No. 1, 2001

42 L. C. ADDING ET AL.

biochemical pharmacology and toxicology of gadolinium is important in view of the in-creasing use of this metal in medicine.

PHARMACOKINETICS

Gadolinium Chelates

The chelating compound determines the pharmacokinetic properties of gadoliniumchelates. As an example, the gadolinium complex of Gd-DTPA is an extremely hydro-philic compound, which after intravenous injection rapidly distributes in the vascularcompartment and diffuses exclusively into the extracellular fluid since it cannot penetratecell membranes. Previous studies have shown that Gd-DTPA does not bind to plasma pro-teins nor interact with other biological structures and is eliminated unmetabolized by thekidneys where excretion is determined by glomerular filtration rate (119,120). However,the results of a recent study indicates that Gd3+ ions in the Gd-DTPA complex can ex-change with Cu2+ and Zn2+ ions under physiological conditions, and that the released Gd3+

may exist in the form of Gd3+-citrate (99).

Gadolinium Chloride

Intravenous administration of CdCl3 to experimental animals causes formation ofmineral emboli in the circulation. Gadolinium chloride at neutral pH can form an in-soluble gadolinium hydroxide colloid (7). The mineral emboli deposit in the capillarybeds of organs, particularly kidney and lung (102,103). These emboli are taken up byphagocytosis by the mononuclear phagocytic system. It has been shown that gadoliniumcan even be found inside the nucleus, indicating that gadolinium in such phagocytosedemboli may redissolve whereupon gadolinium becomes distributed inside the cell (77).Electron-dense deposits found in Kupffer cells, hepatocytes, bile canaliculi, and polymor-phonuclear leukocytes in the liver, pulmonary macrophages, splenic macrophages, bonemarrow macrophages, and mesangial cells of the renal glomerulus have been shown tocontain gadolinium, and may consist of a complex of gadolinium and phosphate (42,69,117). The presence of gadolinium-containing deposits in bile canaliculi has been sug-gested to indicate biliary excretion of the metal (39,117). Experimentally, the intravenousadministration of GdCl3 may require a slow infusion of GdCl3 in order to avoid acute andsevere hypotension leading to cardiovascular collapse, which can occur during adminis-tration. Gadolinium chloride instilled intratracheally in rats can be retained in epitheliallining fluid only to a limited extent in soluble forms and is deposited in the lung tissueprobably in insoluble forms which are metabolized very slowly. The biological half-life ofGdCl3 in the lung was calculated to be 136 days (128).

PHARMACOLOGY

Mechanism of Action

The use of patch clamp recordings from cell membranes has revealed the existence of aclass of stretch-activated ion channels that modulates intracellular ion concentrations in


GADOLINIUM CHLORIDE 43

response to mechanical stimulation (e.g., stretch) and thereby controls cellular function(37). Recently, it was shown that the MID1 gene of the yeast Saccharomyces cerevisiae

encodes as an integral plasma membrane protein required for Ca2+ influx (48). Functionalexpression of this gene product in Chinese hamster ovary cells, mouse Balb�c3T3 cellsand green monkey COS-7 cells reveals a calcium permeable, cation-selective stretch-acti-vated channel (52). Furthermore, at least two (TREK-1 and TRAAK) of the eight different2P domain K+ channels that have been cloned in rodents and humans are stretch-activated(71).

Gadolinium was first used by Millet and Pickard (76) as a possible blocker of stretch-activated calcium channels in plants. Yang and Sachs (127) demonstrated that gadoliniumcompletely blocked stretch-activated cation channels in Xenopus oocytes and GdCl3 is theonly drug that causes a complete and voltage-independent block of many types of stretch-activated ion channels. Other drugs, e.g. amiloride, only produce a partial and highly volt-age-dependent block. Investigations addressing the properties of GdCl3 as an inhibitor ofstretch-activated ion channels are usually performed as electrophysiological whole cell orsingle cell channel recordings. Table 1 lists stretch-induced events in different human cellsthat have efficiently been blocked by GdCl3. Gadolinium maybe a selective inhibitor ofstretch-activated ion channels, but it is definitely not a specific inhibitor. Gadolinium canalso block voltage-gated Ca2+-channels, showing a subtype (L-, T-, and N-type) specificitydepending on the buffer used (11), and voltage-gated Na+ and K+-channels (see Table 2).

The mechanism whereby GdCl3 blocks stretch-activated channels is today not known.Yang and Sachs (127) performed a detailed study of inhibition of Xenopus oocyte stretch-activated channels by GdCl3 and proposed a three step concentration-dependent mech-anism. At low concentrations (1–5 �M) GdCl3 interferes with negative surface chargesnear the opening of the stretch-activated channel. GdCl3 can also bind to an external allo-steric site and thereby causes a transition of the channel to a short-lived closed state. At ahigh concentration (>10 �M) GdCl3 would cause its effects by changing the physical envi-ronment of the membrane channel protein by binding to the lipid bilayer and inducingshifts in phase transitions and decreasing membrane fluidity (37).

One fundamental pathway by which cellular effects are produced involves an increasein the concentration of intracellular calcium. A wide variety of cellular responses, e.g.contraction of muscle cells, transmitter release from neurons and secretion from exocrineand endocrine glands depend on calcium as an intracellular messenger. Because Gd3+ ions



TABLE 1. Human cell types in which stretch-induced cellular responses

have efficiently been blocked by gadolinium

Cell-type Stretch-stimulus Response Reference

Endothelial cells Cyclic stretch Ca2+-influx (57,124)Morphological change (79)

Osteoblasts Fluid shear stress TGF1� production (98)

Lung fibroblasts Uni-axial and cyclic stretch COX II expression (53)

Myocytes Hypotonic swelling Ca2+-influx (50)

Chondrocytes Cyclic pressure Hyperpolarization (123)Neurons, CNS Convex membrane stretch Hyperpolarization (74)

has similarities to Ca2+ ions with respect to size, bonding, coordination and donor atompreference, it is thought that the biochemical effects induced by GdCl3 may occur throughinterference with intracellular calcium-dependent processes and calcium entry into cells.GdCl3 is known to displace Ca2+ from cation-binding sites on cellular membranes (24). Itcan bind to (at high concentrations 0.5–3 mM) and activate the extracellular calcium-sens-ing receptor (107) shown to be present on hepatocytes, kidney, thyroid, and parathyroidgland(s) (18), fibroblasts (2) and pancreas (15). Studies of lipid bilayers confirm thatGdCl3 binds to phospholipids with high affinity and elicits strong electrostatic effects onthe surface of the lipid bilayer thereby inducing structural changes at the membrane�waterinterface (21,30).

Limitations to the Use of Gadolinium Chloride in Experimental Studies

Recently Caldwell and Baumgarten (17) summarized the limitations of using GdCl3 asa pharmacological tool to investigate the involvement of stretch-activated channels. Theyremarked on the chemical interaction of GdCl3 with physiological anions such as phos-phate and carbonate (11), which effectively reduces the free concentration of gadoliniumions in solution and can lead to false negative effects. Additionally, the issue is con-founded by the fact that GdCl3 may also shows some selectivity in its calcium displacingactivity, e.g., GdCl3 does not appear to inhibit the Ca2+-dependent nitric oxide synthaseactivity in guinea pig lung homogenate (6). Apparently GdCl3 has multiple sites of action,all of which have to be considered in order to fully appreciate its pharmacological effects.

Cardiovascular Effects

In 1961 Haley and colleagues (36) investigated the pharmacology of GdCl3 in the anes-thetized cat. They found no observable pharmacological effects by intravenous injectionsof GdCl3 0.5–10 mg�kg. However, GdCl3 20–25 mg�kg produced hypotension and a de-



TABLE 2. Gadolinium block of different ion channels

Ion channel Cell type and species

Blocking

concentration (�M)Refer-ence

Stretch-activated channel Oocyte, Xenopus 10 (127)Ca2+ channel (L-type) Cardiac myocyte, guinea pig 10 (64)

Ca2+ channel (T-type) Pituitary cells, rat 2.5 (11)Ca2+ channel (N-type) Neuronal, rodent 0.5–20 (27)

Acid-sensing ion channel (ASIC) Sensory neuron, human and rat 40 (4)

Ca2+ inactivated Cl– channel Oocytes, Xenopus laevis 20 (85)Store operated Ca2+ channel Liver cells, rat 2 (3)

Na+–Ca2+ exchanger Myocytes, guinea pig 40–100 (130)Na+ channel (voltage) Myelinated nerve, Xenopus laevis 100 (29)

K+ channel (TRAAK) Neurons, CNS, human 10 (74)

K+ channel (delayed rectifier) Myelinated nerve, Xenopus laevis 100 (29)

Table modified from Hamill and McBride, 1996 (37).

crease in femoral blood flow. At 30–50 mg�kg severe cardiac arrhythmias occurred, andelectrocardiographic recordings demonstrated an A-V bundle block and ventricular fibril-lation, eventually leading to complete cardiovascular collapse. Atropine or epinephrinecould not counteract these cardiovascular effects of GdCl3. In accordance with this studywe recently measured similar cardiovascular effects in anesthetized guinea pigs andrabbits in response to slow intravenous infusions of GdCl3 (20–50 mg�kg) (1,6). In rabbitscardiac output and stroke volume decreased continuously throughout the experiments,suggesting a myocardial contractility impairment (Fig. 1). A primary negative inotropiceffect by GdCl3 is possible since GdCl3 has been shown to reduce intracellular calciumtransients (109) and contractility in isolated single rat ventricular myocytes (115), and de-creases length-dependent contractile force of guinea pig papillary muscles (63). Further-more GdCl3 can block the L-type Ca2+-current (64) and the delayed rectifier potassiumcurrent (Ik) in single guinea pig ventricular myocytes (43). Thus GdCl3-sensitive stretch-activated cation channels are likely to be involved in cardiac contractile function and suchchannels have been observed in human cardiac cells (78). Slow intravenous infusions ofGdCl3 (30 mg �kg) did not significantly change the heart rate in anesthetized open-chestrabbits (Fig. 1) though the hearts of these rabbits appeared to be markedly dilated, mostlikely due to the increase in pulmonary vascular resistance (1). Such stretching of the heartmay clinically lead to arrhythmias of significance (25,126). GdCl3, but not the L-type cal-cium channel blockers verapamil, diltiazem or nifedipine, can block stretch-induced ar-rhythmias of isolated canine ventricles (38,105) and rat atrium (110). GdCl3 also inhibitsthe mechanically stimulated increased rate of beating in spontaneously active acutely iso-



FIG. 1. Pentobarbital anesthetized and mechanically ventilated open-chest rabbits. Effects of gadoliniumchloride (GdCl3, 30 mg�kg) on mean arterial blood pressure, heart rate and cardiac output. Bar indicates time ofGdCl3 infusion.

lated embryonic chick heart cells (45). It is likely that GdCl3 exerts its antiarrhythmiceffect by inhibiting stretch-activated channels in excitable cardiac cells. Such stretch-acti-vated channels have been observed in isolated human cardiac cells (78). In addition to theantiarrhythmic effects in stretched hearts, GdCl3 has also been shown to block thestretch-induced secretion of atrial natriuretic peptide (ANP) and to inhibit the pressure-sti-mulated synthesis of B-type natriuretic peptide (BNP) mRNA from isolated superfused ratatria (65,66). Furthermore, coronary blood-flow-, but not acetylcholine-, dependent nitricoxide release from isolated perfused guinea pig heart can efficiently be inhibited by GdCl3(106).

Baroreceptor Neurons

An increase in arterial blood pressure stimulates baroreceptors and increases carotidsinus nerve discharge resulting in inhibition of sympathetic activity. Locally administeredGdCl3 (1 mM) can inhibit baroreceptor activity, within physiological mean arterial bloodpressure ranges (70–150 mm Hg), in anesthetized cats (129) and rabbits (35). Patch-clampstudies performed on baroreceptor neurons indicate that GdCl3 inhibits calcium influxthrough stretch-activated channels and thereby block the mechano-electrical transduction(19,20,22,23). There are no studies reporting the effect of systemically administeredGdCl3 on baroreceptor activity. However, a biphasic decrease in arterial blood pressurehas been reported (1,6,36) and it could be speculated that inhibition of baroreceptor ac-tivity may explain part of this response (Fig. 1). It is interesting to note that aortic endo-thelial cells secrete a diffusible factor that can stimulate the expression of GdCl3-sensitivestretch-activated channels in co-cultured aortic baroreceptor neurons (61). Likewise spon-taneously hypertensive rats have a 4-fold increase in GdCl3-sensitive stretch-activatedchannel density in aortic endothelium and these channels are more sensitive to stretchcompared to stretch-activated channels in normotensive rats (44). Furthermore, humanumbilical vein endothelium from women with pregnancies complicated by preeclampsiahave a two-fold higher density of GdCl3-sensitive stretch-activated channels compared tonormal pregnant women (57). An increased density or mechanosensitivity of stretch-acti-vated ion channels in experimental hypertension of the rat might indicate an altered endo-thelial mechanotransduction (56).

Myocardial Ischemia

Myocardial ischemia and reperfusion injury may cause infarction of cardiac muscleand elicit arrhythmia. In anesthetized dogs a transient dilatation (stretch) of the heart oc-curring just before a sustained myocardial ischemic insult, reduced the infarct size. How-ever, GdCl3 injected into the left atrium, inhibited the stretch-induced cardioprotectiveeffect (82). A similar effect was found in anesthetized rabbits where the involvement ofGdCl3-sensitive stretch-activated channels and downstream activation of PKC, KATP-channels and adenosine receptors were suggested (34). In anesthetized rats pretreatmentwith multiple intramyocardial injections of either saline or adenosine had cardioprotectiveeffects against an ischemic insult. However, multiple intramyocardial injections of GdCl3failed to reduce infarct size (122). During myocardial ischemia a cardiac phospholipaseA2 is activated which converts preferentially plasmalogen to lysoplasmenylcholine(LPLC). It was found that LPLC induced spontaneous contractions in isolated rabbit ven-



tricular myocytes and that GdCl3 effectively blocked this effect and this effect was sug-gested to occur by opposing membrane perturbations caused by LPLC (16). Thus GdCl3inhibits the putative stretch-induced cardioprotective mechanisms that reduce infarct sizeafter myocardial ischemia.

Atrial stretch is known to significantly enhances the vulnerability to atrial fibrillation.A recent study shows that GdCl3 can reduce the stretch-induced fibrillation in a dose-de-pendent manner and the authors of this study suggests that block of stretch activatedchannels might represent a novel antiarrhythmic approach to atrial fibrillation (10).

Pulmonary System

Intravenous administration of GdCl3 induced severe arterial hypoxemia in anesthetizedguinea pigs (6) and rabbits (1). Most likely this was a result of a ventilation-perfusion mis-match due to vasoconstriction and�or microemboli formation in the small pulmonaryvessels since there were no signs of pulmonary edema (1). In fact, GdCl3 can prevent cap-illary leakage and counteract edema formation in the perfused rat lung caused by sustainedhigh airway-pressures (83). Gadolinium chloride did not affect the respiratory rate inspontaneously breathing anesthetized cats (36) and did not change insufflation pressure inmechanically ventilated guinea pigs and rabbits (1,6). Gadolinium chloride can inhibit thebasal, stretch-induced and LPS-induced formation of pulmonary nitric oxide (1,6,32). Fur-thermore, GdCl3 can block stretch-induced upregulation of cyclooxygenase-2 in humanlung fibroblasts, as well as the stretch-induced increase in DNA synthesis and secretion ofglucosaminoglycans that modulate growth activities in fetal pulmonary cells (53,72,125).

Endothelial Cells

Vascular endothelial cells synthesize and secrete a number of vasoactive substances,growth factors and cytokines, play a key role in the interaction with inflammatory cellsand form a barrier to the passage of molecules from the blood to the tissues. These func-tions are strictly regulated by changes in endothelial intracellular calcium concentrationand partly dependent on stretch-activated calcium channels (67). Gadolinium chloride ef-fectively blocks stretch-induced increase in intracellular calcium of endothelial cells (44,78–80,94,124) but also in a variety of other cells including bladder myocytes (121),kidney tubule cells (A6) (54,113), arterial smooth muscle cells (9,100), and pituitarycells (8).

Mononuclear Phagocytic System

Intravenous administration of GdCl3 has a particular effect on the mononuclear phago-cytic system. A single intravenous injection (typically 5–10 mg�kg) inhibits phagocytosisand kills macrophages that are in direct contact with the circulation, such as the Kupffercells of the liver, splenic macrophages and pulmonary intravascular macrophages (39,47,101). GdCl3 can thus be considered a macrophage toxicant, and is used experimentally toinhibit the mononuclear phagocytic system (69). In the rat, intravenous administration ofGdCl3 inhibits phagocytosis by liver macrophages and causes the selective elimination ofthe periportal population of large Kupffer cells (39). At the doses where these effects



occur, little or no direct effect of GdCl3 is seen on other cell types in the liver (60). Alongsimilar lines, it has been shown that livers from GdCl3-treated rats yield 10–30% fewerKupffer cells than do saline-treated rats (92). The depletion of periportal Kupffer cells byGdCl3 leads to an intrahepatic shift of phagocytosis; the more numerous smaller livermacrophages, as well as parenchymal cells, show a relative increase in phagocytotic ac-tivity, although total liver phagocytotic activity is decreased (39,60,70). As a result aninterorgan shift ensues as well: extrahepatic tissues rich in macrophages, such as thespleen and lungs, become more involved in phagocytosis of particulate material in the cir-culation after GdCl3 treatment (39,47). Repopulation of macrophages in the liver startsthree to four days after the administration of GdCl3, and is complete after about one week(39,87). GdCl3 also causes a decrease in the formation of Kupffer cell derived mediators,such as eicosanoids, cytokines, cytokine-induced neutrophil chemoattractant, nitric oxideand reactive oxygen metabolites, both in vivo and in vitro (49) (41,81,84,86,87,93,108).GdCl3 has been shown to exert effects on gene expression. For example, in rats the intra-venous administration of 10 mg�kg GdCl3 reduced mRNA and protein levels of hepaticmicrosomal epoxide hydrolase and glutathione-S-transferase (55). A similar study indi-cated that mRNA and protein levels of cytokine-induced neutrophil chemoattractant werereduced in Kupffer cells isolated from GdCl3-pretreated rats (41). Protein levels of the in-ducible isoform of nitric oxide synthase (iNOS) were reduced in Kupffer cells isolatedfrom GdCl3-pretreated rats (93). Also in activated rat alveolar macrophages GdCl3 de-creased the expression of iNOS (84). Inhibition of mediator formation in macrophages byGdCl3 may lead to a decreased stimulation of gene expression in a neighboring cell type(90). The selective inhibitory effect of GdCl3 on the mononuclear phagocytic system hasallowed many experimental studies on the role of Kupffer cells in, e.g., chemical-inducedhepatotoxicity (28,68,111), endotoxemia (49), ischemia-reperfusion injury (51), portalvenous tolerance (92), and liver tumor surveillance (91). Intravenous administration ofGdCl3 in the rat also induces the transient elimination of red pulp macrophages in thespleen, but there is no effect on white pulp macrophages (39). The interstitial and alveolarmacrophages of the lungs do not appear to be affected functionally by a single intravenousdose of GdCl3 in rats which have, besides receiving GdCl3, not been experimentally chal-lenged by other agents (5,84). However, after in vivo exposure to inhaled ozone or duringendotoxemia the pulmonary macrophages are well inhibited by intravenously adminis-tered GdCl3 (84). Similarly, it has been shown that GdCl3-pretreatment predisposes thelungs to alveolitis induced by administration of lipopolysaccharide in rats (13). Repeatedintravenous administration of GdCl3 to mice has been shown to lead to the presence of ga-dolinium-containing deposits in pulmonary interstitial macrophages (117). It is not knownthough whether interstitial and alveolar macrophages come into contact with GdCl3 after asingle administration of GdCl3 in healthy animals. That this is not the case may be indi-cated by the recent finding that intravenous administration of GdCl3 reduces the numberof pulmonary intravascular macrophages in sheep (101). The depression of macrophagefunction and cell death is likely to occur as a result of the initial phagocytosis of gadolini-um-containing mineral emboli, which form in the circulation when GdCl3 is administeredintravenously. It has been argued that at the acidic pH of phagolysosomes, Gd-containingparticles may redissolve, whereupon gadolinium could disturb intracellular calcium ion-dependent biochemical processes. Inhibition of phagocytosis during blockade of themononuclear phagocytic system with GdCl3 was shown to occur at the level of surface at-tachment and engulfment phases of phagocytosis (47), and by interference with the ED2



receptor on the macrophage cell surface (75). Many of the above described inhibitory ef-fects of GdCl3 observed in vivo are probably due to the physical removal of macrophagesfrom the affected tissues. Furthermore, the vulnerability to GdCl3 seems to depend moreon the phagocytotic capacity of the cells than on their differentiated state (39). Althoughmouse alveolar macrophages in culture take up a larger amount of GdCl3 (by phagocytosisof colloidal GdCl3) than rat macrophages, mouse macrophages are much more resistant toGdCl3 than rat macrophages. This suggests that also dissolution of phagocytosed Gd-colloid in the phagolysosome or subsequent intracellular effects of GdCl3 are importantfactors for the cytotoxicity of GdCl3 to macrophages (62). The mechanism whereby GdCl3kills macrophages in vivo has not been conclusively elucidated. It has been shown thatGdCl3 can induce apoptosis in isolated rat alveolar macrophages in vitro (73,77,114). In

vivo, within several hours of administration of GdCl3 to rats, Kupffer cells start to looselysosomal integrity and loose typical markers of lysosomes and cell surface components.This is accompanied by the loss of phagocytotic activity, the appearance of vacuoles filledwith cellular debris, loss of cellular extensions, and the disappearance of peroxidase ac-tivity in the endoplasmic reticulum and nuclear envelope (58,60). GdCl3 has been shownto be lysosomotropic for macrophages, and the decompartmentalization of lysosomal pro-teinases has been suggested to mediate the cytotoxic effect of phagocytosed GdCl3 par-ticles (59).

Other Effects

Intravenous administration of GdCl3 induces an increase in prothrombin time and acti-vated partial thromboplastin time in rats (103) and markedly decreases circulating plate-lets (103) and leukocytes (1). Intraluminally applied GdCl3 (1–10 mM) decreased choleratoxin-induced fluid secretion in rat jejunum in vivo (112). GdCl3 also reduced catechol-amine release from adrenal medulla cells in vitro (12).

TOXICOLOGY

Toxicity to Humans

Not much is known about the toxicity of gadolinium salts and chelates in humans. Thegadolinium chelates, which are used as contrast agents for magnetic resonance imaginghave low toxicity and the likelihood of free ionized gadolinium reaching toxic concentra-tions in the body is considered to be low, because these chelates are not metabolized (7,26,40). One case report has indicated that the gadolinium-based contrast agent gadoteridol at

a large dose (>0.3 mmol�kg) may have induced acute renal failure in an elderly diabeticpatient with moderately severe renal failure and heavy proteinuria (33). It is unclearwhether free ionized gadolinium or the gadolinium chelate caused this effect itself. Epide-miological data indicate that workers who have been chronically exposed to rare earth ele-ments are at the risk of pneumoconiosis (46,97,116).



Animal Studies

GdCl3 injected at high doses intraperitoneally in mice induces a decreased respiration,lethargy, abdominal cramps and diarrhea. The LD50 at 7 days after exposure was 550mg�kg (36). A similar study indicated an LD50 for intraperitoneally administered gadolini-um nitrate in mice of 300 mg�kg (105 mg gadolinium�kg), and in female rats 230 mg�kg(80 mg gadolinium�kg) (14). There is no lethality up to 2 g�kg when GdCl3 is adminis-tered orally to mice (36). The LD50 for orally administered gadolinium nitrate to femalerats was found to be higher than 5 g�kg (14). Feeding rats during 12 weeks a diet con-taining up to 1% GdCl3 did not affect their growth, hematology or reveal macroscopicsigns of damage to internal organs. Only in male rats at 1% GdCl3 in their diet, perinuclearvacuolization of the liver parenchymal cells and a coarse granularity in the cytoplasm wasshown (36). In rabbits GdCl3 applied into the conjunctival sac can cause ocular irritation.Direct application of GdCl3 to intact rabbit skin does not cause irritation, but intradermaladministration of GdCl3 can lead to erythema, edema and scar formation of the skin. Intra-venous administration of GdCl3 in cats at doses of 30–50 mg�kg can cause immediate car-diovascular collapse (severe hypotension) and death of the animal (36). A single intrave-nous administration of GdCl3 to rats and mice (doses in the order of 10–100 mg�kg) cancause hepatocellular and splenic necrosis, followed by dystrophic mineralization and gra-nulomatous inflammation. It also causes lymphocytolysis. Furthermore, administration ofGdCl3 induces a rapid hypercalcemia and hyperphosphatemia, as well as mineralization ofthe fundic glandular mucosa in the absence of necrosis, followed by mucous cell hyper-plasia (89,102,103). Hepatic alterations such as an increase in the number of non-perfusedsinusoids accompanied by a reduction in bile flow have also been shown to occur (96). Ashort-term study where GdCl3 was administered intravenously at daily doses up to8 mg�kg during two weeks, revealed hepatocellular degeneration associated with a neu-trophilic infiltrate (117). Intratracheal instillation of GdCl3 in the rat lung (10–100 �g�kg)can induce acute lung toxicity, with increased lactate dehydrogenase activity, proteincontent and inflammatory cell count in the bronchoalveolar lavage fluid (BALF). Acutelung toxicity was preceded by an increase of calcium in the BALF supernatant, which maybe derived from blood plasma (128).

SUMMARY

Gadolinium containing compounds are increasingly used in our society. A good under-standing of the pharmacology and toxicology of gadolinium is, therefore, important. Basicexperimental studies have indicated that GdCl3 displays some selectivity in its biochemi-cal and physiological effects. Gadolinium chloride inhibits stretch-activated ion channels,although the mechanism whereby is not clearly understood and other ion channels mayalso be affected. As a result of exposure to GdCl3 a host of physiological alterations can bebrought about, which may be related to interference with the way tissues respond tostretch and with calcium-dependent processes. Other effects, such as the inhibition of themononuclear phagocytic system, may occur in response to the formation of gadolinium-containing particles in body fluids. Although human exposure to gadolinium saltsprobably seldom occurs, toxicity studies have indicated that gadolinium can cause severaldeleterious effects. In the future new drugs may be developed for diseases (e.g., hyper-



tension) where fundamental processes such as cellular mechanotransduction and calciumsignaling are altered. A greater understanding of the biochemical and pharmacologicalproperties of gadolinium may aid this process. Therefore further studies appear warrantedto fully understand the mechanism whereby gadolinium exerts its effects.

REFERENCES

1. Adding LC, Bannenberg GL, Gustafsson LE. Gadolinium chloride inhibition of pulmonary nitric oxide pro-duction and effects on pulmonary circulation in the rabbit. Pharmacol Toxicol 1998;83:8–15.

2. Arthur JM, Lawrence MS, Payne CR, Rane MJ, McLeish KR. The calcium-sensing receptor stimulates JNKin MDCK cells. Biochem Biophys Res Commun 2000;275:538–541.

3. Auld A, Chen J, Brereton HM, Wang YJ, Gregory RB, Barritt GJ. Store-operated Ca2+ inflow in Reuber he-patoma cells is inhibited by voltage-operated Ca2+ channel antagonists and, in contrast to freshly isolated he-patocytes, does not require a pertussis toxin-sensitive trimeric GTP-binding protein. Biochim Biophys Acta

2000;1497:11–26.4. Babinski K, Catarsi S, Biagini G, Seguela P. Mammalian ASIC2a and ASIC3 subunits co-assemble into he-

teromeric proton-gated channels sensitive to Gd3+. J Biol Chem 2000;275:28519–28525.5. Bannenberg G, Lundborg M, Johansson A. Pulmonary macrophage function in systemic gadolinium chlo-

ride-pretreated rats. Toxicol Lett 1995;80:105–107.6. Bannenberg GL, Gustafsson LE. Stretch-induced stimulation of lower airway nitric oxide formation in the

guinea-pig: Inhibition by gadolinium chloride. Pharmacol Toxicol 1997;81:13–18.7. Barnhardt JLKN, Bakan DA, Berk RN. Biodistribution of GdCl3 and Gd-DTPA and their influence on pro-

ton magnetic relaxation in rats tissues. Magn Reson Imaging 1987;5:221–231.8. Biagi BA, Enyeart JJ. Gadolinium blocks low- and high-threshold calcium currents in pituitary cells. Am J

Physiol 1990;259:C515–520.9. Bialecki RA, Kulik TJ, Colucci WS. Stretching increases calcium influx and efflux in cultured pulmonary

arterial smooth muscle cells. Am J Physiol 1992;263: L602–606.10. Bode F, Katchman A, Woosley RL, Franz MR. Gadolinium decreases stretch-induced vulnerability to atrial

fibrillation. Circulation 2000;101:2200–2205.11. Boland LM, Brown TA, Dingledine R. Gadolinium block of calcium channels: Influence of bicarbonate.

Brain Res 1991;563:142–150.12. Bourne GW, Trifaro JM. The gadolinium ion: A potent blocker of calcium channels and catecholamine re-

lease from cultured chromaffin cells. Neuroscience 1982;7:1615–1622.13. Brown AP, Harkema JR, Schultze AE, Roth RA, Ganey PE. Gadolinium chloride pretreatment protects

against hepatic injury but predisposes the lungs to alveolitis after lipopolysaccharide administration. Shock1997;7:186–192.

14. Bruce DW HB, DuBois KP. The acute mammalian toxicity of rare earth nitrates and oxides. Toxicol ApplPharmacol 1963;5:750–759.

15. Bruce JI, Yang X, Ferguson CJ, et al. Molecular and functional identification of a Ca2+ (polyvalent cation)-sensing receptor in rat pancreas. J Biol Chem 1999;274:20561–20568.

16. Caldwell RA, Baumgarten CM. Plasmalogen-derived lysolipid induces a depolarizing cation current inrabbit ventricular myocytes. Circ Res 1998;83:533–540.

17. Caldwell RA, Clemo HF, Baumgarten CM. Using gadolinium to identify stretch-activated channels: Tech-nical considerations. Am J Physiol 1998;275:C619–621.

18. Canaff L, Petit JL, Kisiel M, Watson PH, Gascon-Barre M, Hendy GN. Extracellular calcium-sensing re-ceptor is expressed in rat hepatocytes: Coupling to intracellular calcium mobilization and stimulation of bileflow. J Biol Chem 2001;276:4070–4079.

19. Chapleau MW, Cunningham JT, Sullivan MJ, Wachtel RE, Abboud FM. Structural versus functional modu-lation of the arterial baroreflex. Hypertension 1995;26:341–347.

20. Chapleau MW, Hajduczok G, Sharma RV, et al. Mechanisms of baroreceptor activation. Clin Exp Hypertens1995;17:1–13.

21. Cheng Y, Liu M, Li R, Wang C, Bai C, Wang K. Gadolinium induces domain and pore formation of humanerythrocyte membrane: An atomic force microscopic study. Biochim Biophys Acta 1999;1421:249–260.

22. Cunningham JT, Wachtel RE, Abboud FM. Mechanosensitive currents in putative aortic baroreceptorneurons in vitro. J Neurophysiol 1995;73:2094–2098.

23. Cunningham JT, Wachtel RE, Abboud FM. Mechanical stimulation of neurites generates an inward currentin putative aortic baroreceptor neurons in vitro. Brain Res 1997;757:149–154.



24. De Remedios C. Lanthanide ion probes of calcium-binding sites on cellular membranes. Cell Calcium1986;2:29.

25. Dean JW, Lab MJ. Arrhythmia in heart failure: Role of mechanically induced changes in electrophysiology.Lancet 1989;1:1309–1312.

26. Dean PB, Niemi P, Kivisaari L, Kormano M. Comparative pharmacokinetics of gadolinium DTPA and gado-linium chloride. Invest Radiol 1988;23(Suppl 1):S258–260.

27. Docherty RJ. Gadolinium selectively blocks a component of calcium current in rodent neuroblastoma

� glioma hybrid (NG108–15) cells. J Physiol (Lond ) 1988;398:33–47.28. Edwards MJ, Keller BJ, Kauffman FC, Thurman RG. The involvement of Kupffer cells in carbon tetra-

chloride toxicity. Toxicol Appl Pharmacol 1993;119:275–279.29. Blinder F, Arhem P. Effects of gadolinium on ion channels in the myelinated axon of Xenopus laevis: Four

sites of action. Biophys J 1994;67:71–83.30. Ermakov YuA, Averbakh AZ, Arbuzova AB, Sukharev SI. Lipid and cell membranes in the presence of gad-

olinium and other ions with high affinity to lipids. 2. A dipole component of the boundary potential on mem-branes with different surface charge. Membr Cell Biol 1998;12:411–426.

31. Evans C. Biochemistry of the Lanthanides. New York: Plenum Press, 1990.32. Fujii Y, Goldberg P, Hussain SN. Contribution of macrophages to pulmonary nitric oxide production in

septic shock. Am J Respir Crit Care Med 1998;157:1645–1651.33. Gemery J, Idelson B, Reid S, et al. Acute renal failure after arteriography with a gadolinium-based contrast

agent. Am J Roentgenol 1998;171:1277–1278.34. Gysembergh A, Margonari H, Loufoua J, et al. Stretch-induced protection shares a common mechanism

with ischemic preconditioning in rabbit heart. Am J Physiol 1998;274:H955–964.35. Hajduczok G, Chapleau MW, Ferlic RJ, Mao HZ, Abboud FM. Gadolinium inhibits mechanoelectrical

transduction in rabbit carotid baroreceptors. Implication of stretch-activated channels. J Clin Invest 1994;94:2392–2396.

36. Haley TJRK, Komesu N, Upham HC. Toxicological and pharmacological effects of gadolinium and samari-um chlorides. Br J Pharmacol 1961;17:526–532.

37. Hamill OP, McBride DW Jr. The pharmacology of mechanogated membrane ion channels. Pharmacol Rev

1996;48:231–252.38. Hansen DE, Borganelli M, Stacy GP Jr, Taylor LK. Dose-dependent inhibition of stretch-induced arrhyth-

mias by gadolinium in isolated canine ventricles. Evidence for a unique mode of antiarrhythmic action. CircRes 1991;69:820–831.

39. Hardonk MJ, Dijkhuis FW, Hulstaert CE, Koudstaal J. Heterogeneity of rat liver and spleen macrophages ingadolinium chloride-induced elimination and repopulation. J Leukoc Biol 1992;52:296–302.

40. Harpur ES, Worah D, Hals PA, Holtz E, Furuhama K, Nomura H. Preclinical safety assessment and pharma-cokinetics of gadodiamide injection, a new magnetic resonance imaging contrast agent. Invest Radiol 1993;28(Suppl 1):S28–43.

41. Hisama N, Yamaguchi Y, Ishiko T, et al. Kupffer cell production of cytokine-induced neutrophil chemo-attractant following ischemia�reperfusion injury in rats. Hepatology 1996;24:1193–1198.

42. Hocine N, Berry JP, Jaafoura H, Escaig F, Masse R, Galle P. Subcellular localization of gadolinium injectedas soluble salt in rats: A microanalytical study. Cell Mol Biol 1995;41:271–278.

43. Hongo K, Pascarel C, Cazoria O, Cannier F, Le Guennec JY, White E. Gadolinium blocks the delayed rec-tifier potassium current in isolated guinea-pig ventricular myocytes. Exp Physiol 1997;82:647–656.

44. Hoyer J, Kohler R, Distier A. Mechanosensitive cation channels in aortic endothelium of normotensive andhypertensive rats. Hypertension 1997;30:112–119.

45. Hu H, Sachs F. Mechanically activated currents in chick heart cells. J Membr Biol 1996;154:205–216.46. Husain MH, Dick JA, Kaplan YS. Rare earth pneumoconiosis. J Soc Occup Med 1980;30:15–19.47. Husztik E, Lazar G, Parducz A. Electron microscopic study of Kupffer-cell phagocytosis blockade induced

by gadolinium chloride. Br J Exp Pathol 1980;61:624–630.48. Iida H, Nakamura H, Ono T, Okumura MS, Anraku Y. MID1, a novel Saccharomyces cerevisiae gene en-

coding a plasma membrane protein, is required for Ca2+ influx and mating. Mol Cell Biol 1994;14:8259–8271.

49. Iimuro Y, Yamamoto M, Kohno H, Itakura J, Fujii H, Matsumoto Y. Blockade of liver macrophages bygadolinium chloride reduces lethality in endotoxemic rats — analysis of mechanisms of lethality in endo-toxemia. J Leukoc Biol 1994;55:723–728.

50. Imbert N, Vandebrouck C, Constantin B, et al. Hypoosmotic shocks induce elevation of resting calciumlevel in Duchenne muscular dystrophy myotubes contracting in vitro. Neuromuscul Disord 1996;6:351–360.

51. Jaeschke H, Farhood A. Neutrophil and Kupffer cell-induced oxidant stress and ischemia-reperfusion injuryin rat liver. Am J Physiol 1991;260: G355–362.



52. Kanzaki M, Nagasawa M, Kojima I, et al. Molecular identification of a eukaryotic, stretch-activated non-selective cation channel. Science 1999;285:882–886.

53. Kato T, Ishiguro N, Iwata H, Kojima T, Ito T, Naruse K. Up-regulation of COX2 expression by uni-axialcyclic stretch in human lung fibroblast cells. Biochem Biophys Res Commun 1998;244:615–619.

54. Kawahara K, Matsuzaki K. A stretch-activated cation channel in the apical membrane of A6 cells. Jpn J

Physiol 1993;43:817–832.55. Kim SG, Choi SH. Gadolinium chloride inhibition of rat hepatic microsomal epoxide hydrolase and glutath-

ione S-transferase gene expression. Drug Metab Dispos 1997;25:1416–1423.56. Kohler R, Distler A, Hoyer J. Increased mechanosensitive currents in aortic endothelial cells from genetical-

ly hypertensive rats. J Hypertens 1999;17:365–371.57. Kohler R, Schonfelder G, Hopp H, Distler A, Hoyer J. Stretch-activated cation channel in human umbilical

vein endothelium in normal pregnancy and in preeclampsia. J Hypertens 1998;16:1149–1156.58. Korolenko T, Svechnikova I, Urazgaliyev K, Vakulin G, Djanaeva S. Liver cysteine proteinases in macro-

phage depression induced by gadolinium chloride. Adv Exp Med Biol 1997;421:315–321.59. Korolenko TA, Svechnikova IG. [Regulation of liver cysteine proteinases during macrophagal stimulation

and depression]. Vestn Ross Akad Med Nauk 1998;10:26–29.60. Koudstaal JDF, Hardonk MJ. Selective depletion of Kupffer cells after intravenous injection of gadolini-

umchloride. In: Wisse EKD, McCuskey RS, Eds. Cells of the Hepatic Sinusoid. The Netherlands: KupfferCell Foundation, 1991.

61. Kraske S, Cunningham JT, Hajduczok G, Chapleau MW, Abboud FM, Wachtel RE. Mechanosensitive ionchannels in putative aortic baroreceptor neurons. Am J Physiol 1998;275:H1497–1501.

62. Kubota Y, Takahashi S, Takahashi I, Patrick G. Different cytotoxic response to gadolinium between mouseand rat alveolar macrophages. Toxicol Vitr 2000;14:309–319.

63. Lab MJ, Zhou BY, Spencer CI, Homer SM, Seed WA. Effects of gadolinium on length-dependent force inguinea-pig papillary muscle. Exp Physiol 1994;79:249–255.

64. Lacampagne A, Cannier F, Argibay J, Gamier D, Le Guennec JY. The stretch-activated ion channel blockergadolinium also blocks L-type calcium channels in isolated ventricular myocytes of the guinea-pig. Biochim

Biophys Acta 1994;1191:205–208.65. Laine M, Arjamaa O, Vuolteenaho O, Ruskoaho H, Weckstrom M. Block of stretch-activated atrial natri-

uretic peptide secretion by gadolinium in isolated rat atrium. J Physiol (Lond ) 1994;480:553–561.66. Laine M, Id L, Vuolteenaho O, Ruskoaho H, Weckstrom M. Role of calcium in stretch-induced release and

mRNA synthesis of natriuretic peptides in isolated rat atrium. Pflügers Arch 1996;432:953–960.67. Lansman JB, Hallam TJ, Rink TJ. Single stretch-activated ion channels in vascular endothelial cells as me-

chanotransducers? Nature 1987;325:811–813.68. Laskin DL, Gardner CR, Price VF, Jollow DJ. Modulation of macrophage functioning abrogates the acute

hepatotoxicity of acetaminophen. Hepatology 1995;21:1045–1050.69. Lazar G. The reticuloendothelial-blocking effect of rare earth metals in rats. J Reticuloendothel Soc

1973;13:231–237.70. Lazar G, van Galen M, Scherphof GL. Gadolinium chloride-induced shifts in intrahepatic distributions of

liposomes. Biochim Biophys Acta 1989;1011:97–101.71. Lesage F, Lazdunski M. Molecular and functional properties of two-pore-domain potassium channels [In

Process Citation]. Am J Physiol Renal Physiol 2000;279: F793–801.72. Liu M, Xu J, Tanswell AK, Post M. Inhibition of mechanical strain-induced fetal rat lung cell proliferation

by gadolinium, a stretch-activated channel blocker. J Cell Physiol 1994;161:501–507.73. Lizon C, Fritsch P. Chemical toxicity of some actinides and lanthanides towards alveolar macrophages: An

in vitro study. Int J Radiat Biol 1999;75:1459–1471.74. Maingret F, Fosset M, Lesage F, Lazdunski M, Honore E. TRAAK is a mammalian neuronal mechano-gated

K+ channel. J Biol Chem 1999;274:1381–1387.75. Martin S. Changes in Kupffer cell phenotype and acinar location induced by intravenous gadolinium

chloride. In: Knook DL WE, Ed. Cells of the Hepatic Sinusoid. The Netherlands: Kupffer Cell Foundation,1993;168–170.

76. Millet BPB. Gadolinium ion is the inhibitor suitable for testing the putative role of stretch-activated ionchannels in geotropism and thigmotropism. Biochem J 1988;53:155.

77. Mizgerd JP, Molina RM, Steams RC, Brain JD, Wamer AE. Gadolinium induces macrophage apoptosis. JLeukoc Biol 1996;59:189–195.

78. Naruse K, Sokabe M. Involvement of stretch-activated ion channels in Ca2+ mobilization to mechanicalstretch in endothelial cells. Am J Physiol 1993;264:C1037–1044.

79. Naruse K, Yamada T, Sai XR, Hamaguchi M, Sokabe M. Pp125FAK is required for stretch dependent mor-phological response of endothelial cells. Oncogene 1998;17:455–463.



80. Naruse K, Yamada T, Sokabe M. Involvement of SA channels in orienting response of cultured endothelialcells to cyclic stretch. Am J Physiol 1998;274: H1532–1538.

81. O’Neill PJ, Ayala A, Wang P, et al. Role of Kupffer cells in interleukin-6 release following trauma-hemor-rhage and resuscitation. Shock 1994;1:43–47.

82. Ovize M, Kloner RA, Przyklenk K. Stretch preconditions canine myocardiurn. Am J Physiol

1994;266:H137–146.83. Parker JC, Ivey CL, Tucker JA. Gadolinium prevents high airway pressure-induced permeability increases

in isolated rat lungs. J Appl Physiol 1998;84:1113–1118.84. Pendino KJ, Meidhof TM, Heck DE, Laskin JD, Laskin DL. Inhibition of macrophages with gadolinium

chloride abrogates ozone-induced pulmonary injury and inflammatory mediator production. Am J Respir

Cell Mol Biol 1995;13:125–132,85. Perez-Samartin AL, Miledi R, Arellano RO. Activation of volume-regulated Cl– channels by ACh and ATP

in Xenopus follicles. J Physiol 2000;525(3):721–734.86. Püschel GP, Nolte A, Schieferdecker HL, Rothermel E, Götze O, Jungermann K. Inhibition of anaphyla-

toxin C3a- and C5a- but not nerve stimulation- or noradrenaline-dependent increase in glucose output andreduction of flow in Kupffer cell-depleted perfused rat livers. Hepatology 1996;24:685–690.

87. Rai RM, Zhang JX, Clemens MG, Diehl AM. Gadolinium chloride alters the acinar distribution of phago-cytosis and balance between pro- and anti-inflammatory cytokines. Shock 1996;6:243–247.

88. Reedijk J. Medicinal applications of heavy-metal compounds. Curr Opin Chem Biol 1999;3:236–240.89. Rees J, Spencer A, Wilson S, Reid A, Harpur E. Time course of stomach mineralization, plasma, and uri-

nary changes after a single intravenous administration of gadolinium (111) chloride in the male rat. ToxicolPathol 1997;25:582–589.

90. Rizzardini M, Zappone M, Villa P, et al. Kupffer cell depletion partially prevents hepatic heme oxygenase 1messenger RNA accumulation in systemic inflammation in mice: Role of interleukin 1beta. Hepatology

1998;27:703–710.91. Roh MS, Kahky MP, Oyedeji C, et al. Murine Kupffer cells and hepatic natural killer cells regulate tumor

growth in a quantitative model of colorectal liver metastases. Clin Exp Metastasis 1992;10:317–327.92. Roland CR, Mangino MJ, Duffy BF, Flye MW. Lymphocyte suppression by Kupffer cells prevents portal

venous tolerance induction: A study of macrophage function after intravenous gadolinium. Transplantation

1993;55:1151–1158.93. Roland CR, Naziruddin B, Mohanakumar T, Flye MW. Gadolinium chloride inhibits Kupffer cell nitric

oxide synthase (iNOS) induction. J Leukoc Biol 1996;60:487–492.94. Rosales OR, Isales CM, Barrett PQ, Brophy C, Sumpio BE. Exposure of endothelial cells to cyclic strain

induces elevations of cytosolic Ca2+ concentration through mobilization of intracellular and extracellularpools. Biochem J 1997;326:385–392.

95. Runge VM. Contrast media research. Invest Radiol 1999;34:785–790.96. Ruttinger D, Vollmar B, Wanner GA, Messmer K. In vivo assessment of hepatic alterations following gado-

linium chloride-induced Kupffer cell blockade. J Hepatol 1996;25:960–967.97. Sabbioni E, Pietra R, Gaglione P, et al. Long-term occupational risk of rare-earth pneumoconiosis. A case

report as investigated by neutron activation analysis. Sci Total Environ 1982;26:19–32.98. Sakai K, Mohtai M, Iwamoto Y. Fluid shear stress increases transforming growth factor beta 1 expression

in human osteoblast-like cells: Modulation by cation channel blockades. Calcif Tissue Int 1998;63:515–520.

99. Sarka L, Burai L, Brucher E. The rates of the exchange reactions between [Gd(DTPA)]2– and the endo-genous ions Cu2+ and Zn2+: A kinetic model for the prediction of the in vivo stability of [Gd(DTPA)]2–, usedas a contrast agent in magnetic resonance imaging. Chemistry 2000;6:719–724.

100. Setoguchi M, Ohya Y, Abe I, Fujishima M. Stretch-activated whole-cell currents in smooth muscle cellsfrom mesenteric resistance artery of guinea-pig. J Physiol (Lond ) 1997;501:343–353.

101. Singh B, de la Concha-Bermejillo A. Gadolinium chloride removes pulmonary intravascular macrophagesand curtails the degree of ovine lentivirus-induced lymphoid interstitial pneumonia. Int J Exp Pathol

1998;79:151–162.102. Spencer A, Wilson S, Harpur E. Gadolinium chloride toxicity in the mouse. Human Exp Toxicol

1998;17:633–637.103. Spencer AJ, Wilson SA, Batchelor J, Reid A, Rees J, Harpur E. Gadolinium chloride toxicity in the rat.

Toxicol Pathol 1997;25:245–255.104. Spinosa DJ, Matsumoto AH, Hagspiel KD, Angle JF, Hartwell GD. Gadolinium-based contrast agents in

angiography and interventional radiology. Am J Roentgenol 1999;173:1403–1409.105. Stacy GP Jr, Jobe RL, Taylor LK, Hansen DE. Stretch-induced depolarizations as a trigger of arrhythmias

in isolated canine left ventricles. Am J Physiol 1992;263:H613–621.





106. Suarez J, Torres C, Sanchez L, del Valle L, Pastelin G. Flow stimulates nitric oxide release in guinea pigheart: Role of stretch-activated ion channels. Biochem Biophys Res Commun 1999;261:6–9.

107. Takeyama S, Yoshimura Y, Shirai Y, et al. Low calcium environment effects osteoprotegerin Ligand�Os-teoclast differentiation factor [In Process Citation]. Biochem Biophys Res Commun 2000;276:524–529.

108. Tapia G, Troncoso P, Galleano M, Femandez V, Puntarulo S, Videla LA. Time course study of the influenceof acute iron overload on Kupffer cell functioning and hepatotoxicity assessed in the isolated perfused ratliver. Hepatology 1998;27:1311–1316.

109. Tatsukawa Y, Kiyosue T, Arita M. Mechanical stretch increases intracellular calcium concentration in cul-tured ventricular cells from neonatal rats. Heart Vessels 1997;12:128–135.

110. Tavi P, Laine M, Weckstrom M. Effect of gadolinium on stretch-induced changes in contraction and intra-cellularly recorded action- and afterpotentials of rat isolated atrium. Br J Pharmacol 1996;118:407–413.

111. Thurman RG. II. Alcoholic liver injury involves activation of Kupffer cells by endotoxin. Am J Physiol1998;275:G605–611.

112. Timar Peregrin A, Svensson M, Jodal M, Lundgren O. Calcium channels and intestinal fluid secretion: Anexperimental study in vivo in rats. Acta Physiol Scand 1997;160:371–378.

113. Urbach V, Leguen I, O’Kelly I, Harvey BJ. Mechanosensitive calcium entry and mobilization in renal A6cells. J Membr Biol 1999;168:29–37.

114. van Rooijen N, Sanders A. Elimination, blocking, and activation of macrophages: Three of a kind? JLeukoc Biol 1997;62:702–709.

115. Ward H, White E. Reduction in the contraction and intracellular calcium transient of single rat ventricularmyocytes by gadolinium and the attenuation of these effects by extracellular NaH

2PO

4. Exp Physiol

1994;79:107–110.116. Waring PM, Watling RJ. Rare earth deposits in a deceased movie projectionist. A new case of rare earth

pneumoconiosis? Med J Aust 1990;153:726–730.117. Wasserman AJ, Monticello TM, Feidman RS, Gitlitz PH, Durham SK. Utilization of electron probe micro-

analysis in gadolinium-treated mice. Toxicol Pathol 1996;24:588–594.118. Weinmann H, Press W, Raduchel B, Platzek J, Schmitt-Willich H, Vogler H. Characterstics of Gd-DTPA

and new derivatives. In: Bydder G et al., Eds. Contrast Media in MRI. Bussum, The Netherlands: MedicomEurope B.V., 1990.

119. Weinmann HJ, Brasch RC, Press WR, Wesbey GE. Characteristics of gadolinium-DTPA complex: A po-tential NMR contrast agent. Am J Roentgenol 1984;142:619–624.

120. Weinmann HJ, Laniado M, Mutzel W. Pharmacokinetics of GdDTPA�dimeglumine after intravenous in-jection into healthy volunteers. Physiol Chem Phys Med NMR 1984;16:167–172.

121. Wellner MC, Isenberg G. Stretch-activated nonselective cation channels in urinary bladder myocytes: Im-portance for pacemaker potentials and myogenic response. Exs 1993;66:93–99.

122. Whittaker P, Kloner RA, Przyklenk K. Intramyocardial injections and protection against myocardial ische-mia. An attempt to examine the cardioprotective actions of adenosine. Circulation 1996;93:2043–2057.

123. Wright M, Jobanputra P, Bavington C, Salter DM, Nuki G. Effects of intermittent pressure-induced strainon the electrophysiology of cultured human chondrocytes: Evidence for the presence of stretch-activatedmembrane ion channels. Clin Sci (Colch) 1996;90:61–71.

124. Wung BS, Cheng JJ, Chao YJ, Lin J, Shyy YJ, Wang DL. Cyclical strain increases monocyte chemotacticprotein-1 secretion in human endothelial cells. Am J Physiol 1996;270:H1462–1468.

125. Xu J, Liu M, Liu J, Caniggia I, Post M. Mechanical strain induces constitutive and regulated secretion ofglycosaminoglycans and proteoglycans in fetal lung cells. J Cell Sci 1996;109:1605–1613.

126. Yang X. Characterization of stretch-activated ion channels in Xenopus oocytes. SUNYAB, 1989.127. Yang XC, Sachs F. Block of stretch-activated ion channels in Xenopus oocytes by gadolinium and calcium

ions. Science 1989;243:1068–1071.128. Yoneda S, Emi N, Fujita Y, Ohmichi M, Hirano S, Suzuki KT. Effects of gadolinium chloride on the rat

lung following intratracheal instillation. Fund Appl Toxicol 1995;28:65–70.129. Zanzinger J, Czachurski J, Seller H. Lack of nitric oxide sensitivity of carotid sinus baroreceptors activated

by normal blood pressure stimuli in cats. Neurosci Lett 1996;208:121–124.130. Zhang YH, Hancox JC. Gadolinium inhibits Na+-Ca2+ exchanger current in guinea-pig isolated ventricular

myocytes. Br J Pharmacol 2000;130:485–488.

Documents

Gadolinium Salts and Its Chelates -Clinical-experimental Studies