Abstrarts 429

Trypan blue, which disrupts protein uptake and degradation in VYS, reduced the uptakes of both Bi2 and TCII-Bi2 in a dose related manner [OS mg/ml: in vitro - 72 per cent (Biz) and - 56 per cent (TCIIBi& in vivo - 59 per cent (Btz) and -76 per cent (TCIIB,,); 0.05 mg/ml: in vitro - 23 per cent (Biz) and - 15 per cent (TCIIB1z), in vivo - 12 per cent (Bi2) and - 23 per cent (TCIIBiz)]. Colchicine, a microtubule poison, also reduced both uptakes [0.05 mg/ml: in vitro - 26 per cent (Blz) and - 37 per cent (TCIIBiz), in vivo - 32 per cent (B1z) and -41 per cent (TCIIBi2)]. H owever, ouabin, an inhibitor of Na + K-ATPase, at (7.3 /kg/ml) did not inhibit uptake of either B iz in vitro or in vivo. Incubation at 4°C did reduce Biz and TCIIBiz uptakes by - 78 per cent and - 68 per cent respectively. Thus, vitamin Biz transport via the VYS is apparently regulated by similar endocytotic processes as proposed for proteins. (Supported by NIH ES02774.)

THE PLACENTAL RELEASE OF HUMAN CHORIONIC GONADOTROPIN AND PLACENTAL LACTOGEN IS STIMULATED IN VITRO BY EXTRACELLULAR SODIUM REMOVAL B. Polliotti, P. Lebrun, C. Robyn & S. Meuris (Human Reproduction Research Unit and Laboratory of Pharmacology, Free University of Brussels (ULB), B-1000 Brussels, Bel- gium)

Recent findings clearly indicate that Ca2+ plays a major role in the secretory process of human chorionic gonadotropin (hCG) and placental lactogen (hPL). The purpose of the study was to investigate the effects of extracellular sodium omission [Na+]o, another cation involved in ionic homeostasis of living cells, on the release of these hormones.

Explants dissected from placentae obtained from normal term pregnancies were incubated in Krebs-Ringer solutions buffered with Hepes. The media were changed every 30 min and radioimmunoassayed for hCG and hPL. Isoosmotic replacement of [Na+]o by sucrose, K+ or choline stimulated the hCG and hPL release. This effect was concentration-dependent, inhibited in the absence of extracellular Ca2+ and impaired in the presence of Co2’ (0.5 m@. The stimulatory effect of [Na+]o was not modified by blockers of the voltage- sensitive Ca2+ channels, nifedipine (20 PM) and D600 (50 PM), nor by a specific blocker of the Na+ channel, tetrodotoxin (5 PM). Amiloride (2 mM), M$+ (10 mM) and Sr2+ (10 mhl), which are known to affect the Na+/Ca2+ exchange, impaired the stimulatory effect of [Nai lo. Ouabain (2 mu), an inhibitor of the Na+/K+-ATPase enhanced the secretory response to [Naf]o.

These findings indicate that [Na+]o induces a Ca2+ -dependent stimulation of the hCG and hP1. release. The pharmacological analysis of the secretory effects of Na+ deprivation suggest the existence of a process of Na+/Ca2’ exchange in placental cells.

EFFECT OF CALCITONIN ON TROPHOBLAST CELLS IN VITRO C. Rebut-Bonneton, J. Demignon, N. Segond” & D. Evain-Brion (URA 1337,46 rue d’LJlm 75005 Paris and a U 113,27 rue Chaligny, 75011 Paris, France)

Most of the specialized functions of the placenta are carried out by a broad outer layer of syncytiotrophoblasts which arise from the fusion of stem cells, cytotrophoblasts. In vitro

430 Placenta (1991), Vol. 12

studies have demonstrated that the endocrine function of cytotrophoblasts can be stimulated by a CAMP dependent mechanism. The description of receptors for calcitonin (CT) prompted us to investigate the effects of CT with respect to CAMP levels and hCG secretion in cultivated cells from first trimester and term placenta and in a choriocarcinoma cell line JEG-3. Addition of physiological concentrations of salmon or human CT resulted in an increase in CAMP secretion by normal trophoblast cells. Physiological concentrations of CT increased CAMP levels and hCG synthesis preferentially in late culture i.e. on completely differentiated syncytiotrophoblasts. The CT effects on the choriocarcinoma cells were found to be lower than on early cultured normal cytotrophoblast cells.

In conclusion CT is most effective in terms of hCG and CAMP production in more highly differentiated cytotrophoblasts.

BIDIRECTIONAL HUMAN PLACENTAL GLUCOSE TRANSFER IN VITRO PREFERS MATERNOFETAL DIRECTION W. Reiber, A. Malek, E. Aegerter, R. Sager 8s H. Schneider [Departments of Obstetrics/ Gynecology, University of Jena (FRG) and Berne (CH)]

The aim of the study was to investigate bidirectional glucose transfer across the isolated dually perfused human placental lobule with different concentration gradients.

Maternofetal transfer was examined in ten experiments (M + F group) with five different concentration gradients, where maternal glucose levels were constant (6.7 mmol/l) and fetal concentrations varied (6.7; 5.6; 4.4; 3.3; and 1.8 mmol/I). In another ten perfusions (F + M group) gradients were reversed, with constant fetal glucose concentration (6.7 mmol/l) and varying maternal levels. In both groups the non-metabolizable 3H-labelled D-deoxyglucose and 14C-labelled L-glucose were added to that circuit where D-glucose levels were constantly 6.7 mmol/l.

For each gradient step D-glucose transfer was significantly higher in M + F experiments compared to F -+ M group. Transfer rate and gradient were positively correlated in both transfer directions. Glucose uptake from donor circuit was also higher in M + F than in reverse direction, although the difference was significant in only one gradient step. Placental glucose consumption was equal in both groups and was independent from the gradient (mean 0.20 ~moVmin/g). Transfer of 3H-D-deoxyglucose was significantly higher in the M --+ F

group. “C-L-glucose transfer rates were independent of transfer direction. The results indicate a possible protective effect of the placenta against glucose loss of the fetus under maternal hypoglycemia. (Supportedby Swiss National Foundation and W. Sander-Stiftung.)

MONOCLONAL ANTIPHOSPHOLIPID ANTIBODIES REACT WITH HUMAN TROPHOBLAST N. S. Rote, T. W. Lyden & E. Vogt (Departments of Microbiology/Immunology and Obstetrics/Gynecology, Wright State University School of Medicine, Dayton, OH 45435, USA)

Naturally occurring autoantibodies against phospholipids, especially cardiolipin (CL) and phosphatidylserine (PS), are strongly associated with recurrent pregnancy loss, early and