5. V. Tanphaichitr, M. S. Zaklama and H.P. Bro- quist: Dietary Lysine and Carnitine: Relation to Growth and Fatty Livers in Rats. J. Nutrition

6. P. R. Borum and H. P. Broquist: Lysine Defi- ciency and Carnitine in Male and Female Rats. J. Nutrition 107: 1209-1215, 1977

7. G. Cederblad: Plasma Carnitine and Body Com- position. Clin. Chim. Acta 67: 207-212, 1976

8. S.W. Chu and D. M. Hegsted: Adaptive Re- sponses of Lysine and Threonine Degrading Enzymes in Adult Rats. J. Nutrition 106:

9. V. Tanphaichitr and H.P. Broquist: Role of Ly- sine and e-N-Trimethyllysine in Carnitine Bio- synthesis. Studies in the Rat. J. Biol. Chem. 248: 21762181, 1973

10. G. Lindstedt: Hydroxylation of y-butyrobetaine to Carnitine in Rat Liver. Biochemistry 6: 1271- 1282, 1967

106: 111-117, 1976

1089-1096, 1976

11. W.K. Paik and S. Kim: Protein Methylation: Chemical, Enzymological and Biological Sig- nificance. Adv. Enzymol. 42: 227-286, 1975

12. J. LaBadie, W.A. Dunn and N. N. Aronson, Jr.: Hepatic Synthesis of Carnitine from Pro- tein-Bound Trimethyl-Lysine. Lysosomal Di- gestion of Methyl-Lysine-Labelled Asialo- Fetuin. Biochem. J. 160: 85-95, 1976

13. H. T. Haigler and H. P. Broquist: Carnitine Syn- thesis in Rat Tissue Slices. Biochem. Biophys. Res. Commun. 56: 676681, 1974

14. J. D. Hulse, S. R. Ellis and L. M. Henderson: Carnitine Biosynthesis. p-Hydroxylation of Trimethyllysine by an a-Ketoglutarate-Depend- ent Mitrochondrial Dioxygenase. J. Biol. Chem. 253: 1654-1659, 1978

15. R. A. Kaufman and H. P. Broquist: Biosynthe- sis of Carnitine in Neurospora crassa. J. Biol. Chem. 252: 7437-7439. 1977

INTESTINAL ABSORPTION OF ADENOSINE TRIPHOSPHATE

Adenosine triphosphate (ATP) is split to dephosphorylated adenine nucleotides and nucleosides before carrier-mediated passage through the gut

wall. Hvdrolysis of ATP to adenosine appears to be coupled to transport.

Key Words: adenosine triphosphate (ATP), ADP, AMP, adenosine, carrier-mediated transport, small intestine

and then resynthesized in the Cell? A recent in vitro study has dealt with the mechanism of ATP absorption by the small intestine from rabbits.

Isotopic ATP labeled either in the purine moiety with tritium or in the 7-phosphate group with P32 was utilized in these studies to demon- strate entry of adenine nucleotides and nucleo- sides into cells. ATP entry into the intestine mucosal cells was dependent on concentra- tion of ATP in the medium. At concentrations between 50 pM and 3 mM, the kinetics of ATP entry were non-linear approximating the Michaelis-Menton plot. At concentrations in excess of 3 mM, influx of ATP was linear. The linear component above 3 mM probably repre-

Absorption of most of the major nutrients by the intestine has been extensively studied. Little attention, however, has been given to the investigation of the mechanism of absorption of purines, nucleotides, nucleosides, and their bases. This class of compounds includes the precursors of nucleic acids and some co- enzymes. Has the absorption of bound forms of vitamins contributed to the nutrient require- ments of these vitamins? Are adenine nucleo- tides absorbed as such, or are they hydrolyzed

NUTRITION REVIEWS I VOL. 36. NO. 10 OCTOBER 1978 309

sented diffusional entry of the labeled com- pounds into the cells.

Because ATP undergoes hydrolysis at the microvillar membrane surface to yield progres- sively ADP, AMP and adenosine, the kinetics of (CIS) adenosine were measured under con- ditions similar to those for ATP. Adenosine en- try exhibited saturation kinetics at low concen- trations and resembled closely the results ob- tained for ATP. When 5 mM adenosine was added to the medium, inhibition of labeled ATP uptake was less than predicted from an as- sumption of a common carrier. When (y-P32) ATP was used, it was found that most of the phosphate was removed and the entry of the remaining P32 could have been taken by the known separate pathway for inorganic phos- phate. Entry of the (3H)-adenine portion of the substrate into cells was shown by radioau- tography .

The well-known dependence of the amino acids and sugars on the ionic composition of mucosal fluid was not evident for ATP. Adenine nucleotide transport is not dependent on sodium, which is so necessary for amino acid and glucose absorption. Nucleotide transport was also independent of magnesium and cal- cium even though these substances form stable complexes with ATP. Inhibitors of ATP transport were also studied. Persantin which blocks the absorption of adenosine in lung and heart tissue and atractyloside which in- hibits the ATP-ADP exchange in mitochondria were studied. Neither of these substances af- fected ATP uptake by intestinal cells. The role of known hydrolytic enzymes was examined using L-phenylalanine which has been shown to inhibit alkaline phosphatase. At a concentra- tion of 50 mM, tenfold higher than that required to completely inhibit isolated alkaline phospha- tase, no effect of L-phenylalanine on ATP up- take was demonstrable. The general enzyme inhibitor p-toluquinone inhibited the non- linear accumulation of ATP but had no effect on the linear component. The addition of nucleotides and nucleosides structurally re- lated to ATP did inhibit ATP transport but adenine did not, indicating that the minimum requirement for this transport system was a nucleoside. GTP, ITP and the purine ribo- sides 2-deoxyadenosine and 6chloropurine 310 NWRlTlON REYEWS I VOL. 36, NO. 10 OCTOBER 1978

riboside all were inhibitory. The pyrimidine nucleotide CTP and its nucleoside did not in- hibit ATP absorption.

These data indicate that at low concentra- tions of adenine nucleotides and nucleosides in the chyme, there is a carrier mediated trans- port of ATP and its dephosphorylation products by the gut. Since the entry of these metabo- lites are mutually inhibitory, a common carrier mediated mechanism of the transport of ATP and adenosine into cells is suggested. The structural requirements for competitive in- hibition indicate that a purine ring bonded to ribose is required. Substitutions at the C-6 PO- sition of the purine ring did not appear to be a critical determinant of transport specificity. Carrier-mediated transport of purine nucleo- sides has been shown in the erythrocyte.2

This carrier-mediated transport of adenine nucleosides across gut and erythrocyte mem- branes is clearly diff erent from the ATP-ADP exchange across the inner membrane of mitochondria.3 In this transport system the ATP and ADP are transported intact by an electrogenic mechanism which has an exqui- site specificity.

One of the major unsolved problems in intes- tinal physiology is the relationship between hydrolysis and transport of nutrients. Mea- surements of the uptake of glucose derived from sucrose by the gut show that the derived glucose appears in the cells and not in the m0diurn.O Similarly the absorption of amino acids from peptides is greater than that ex- pected from the free amino acid concentration.5 In the case of ATP, Harms and Stirling' have shown that adenosine found in the bulk solution could not account for all the ATP absorbed. Moreover, adenosine in the medium did not inhibit radiolabeled ATP entry to the degree expected. It would appear that ATP absorption is a further example of the phenomenon in which intestinal hydrolysis of a substrate and absorption of the products are linked to facili- tate entry of the hydrolytic product into cells.

It is clearly established that ATP synthesis in cells in mammals is independent of dietary requirements for its organic components, name- ly adenine and ribose. On %ofher hand, the fact that adenosine is consenred during absorp- tion of ATP by the gut illustrates the wisdom

of the body achieving some energy conserva- tion. 0

1. V. Harms and C.E. Stirling: Transport of Purine Nucleotides and Nucleosides by In Vitro Rabbit Ileum. Am. J. Physiol. 223E47-#55, 1977

Transport of Nucleosides in Human Erythrocytes. J. Biol. Chem. 247: 33143320, 1072

3.

4.

2. C.E. Cass and A.R.P. Paterson: Mediated 5.

M. Klingenberg in The Enzymes of Biological Membranes. A. Martonosi, Editor, pp. 383438. Plenum Publishing Cop., New York, 1976 D. Miller and R.K. Crane: The Digestive Func- tion of the Epithelium of the Small Intestine. Biochim. Biophys. Acta. 52: 281-293, 1961 G.M. Gray and H.L. Cooper: Protein Digestion and Absorption. Gastroenterology 61: 535544, 1971

IMMUNE RESPONSE TO BCG AND TYPHOID VACCINES IN NUTRITIONALLY DEPRIVED MICE

Mice fed hatf the quantity of food consumed by a control group showed less frequent and poor response to BCG vaccine but produced

normal antibody levels to typhoid-paratyphoid vaccine.

Key Words: calorie deficiency, cell-mediated im- munity, immunization, antibody response

The common and frequently coexisting health problems of nutritional deficiency and infec- tious diseases have stimulated many studies investigating the mechanisms involved.' v 2

The clinical and epidemiologic information obtained in subtropical and tropical countries suggests that host resistance of undernour- ished individuals is impaired. It is documented that such secondary deficiency of immunity function is generally easily reversed by nutri- tional therapy, except in fetal growth retarda- tion. At the same time, the very same social, cultural and economic factors contributing to nutritional deficiency also maintain a high inci- dence of infections. Most of the studies of im- mune response in malnutrition focused on the effect of protein deficiency, whereas on a glo- bal scale, calorie deficiency manifesting as marasmus, small stature and failure to thrive is a much more frequent clinical problem.

The discrepancies in results of observations in man have stimulated controlled experiments with animals. In a recent report, Narayanan et al.3 studied the immunologic responsive-

ness of undernourished mice to two commonly used vaccines, BCG and typhoid-paraty- phoid and A and B (TAB). Male swiss mice were randomly divided into experimental and control groups. Both groups were fed a diet consisting of chapati (flat bread rolled and baked from dough of wheat flour) and black grams that had been soaked in water and al- lowed to germinate for 24 hours and subse- quently washed. Control mice were given this food ad libitum whereas animals in the experi- mental group received half the amount esti- mated to be consumed by the former. Immuni- zation was achieved either by the intraperi- toneal injection of 1 mg wet weight of BCG sus- pended in 0.2 ml of bovine serum albumin sal- ine per 25 g of body weight, or by the sub- cutaneous injection of 108 bacilli per 25 g of body weight. Observations were made for eight weeks. Delayed hypersensitivity was assessed by the response to foot pad injection of 10 pg of purified protein derivative in 50 pl of 10-mmole per liter phosphate buffered saline. Antibody titer was estimated by standard ag-

glutination techniques. Caloriedeprived mice lost weight initially but thereafter maintained a low but steady body weight. There was no

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