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Folate transport in enterocytes and brush-border-membrane vesicles isolated from the small intestine of the neonatal goat

Published online by Cambridge University Press:  09 March 2007

Peter Blakeborough  and
Dallyn N. Salter
Peter Blakeborough
Affiliation:
Department of Food Quality and Human Nutrition, AFRC Institute of Food Research, Reading Laboratory, Shinfield, Reading RG2 9AT
Dallyn N. Salter
Affiliation:
Department of Pig Nutrition and Production, AFRC Institute of Grassland and Animal Production, Shinfield, Reading RG2 9AQ
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Abstract

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1. The uptake of 5-methyltetrahydrofolate (MTHF) and folic acid (pteroylmonoglutamate) by enterocytes and brush-border-membrane vesicles prepared from the small intestine of the 6-d-old male goat was determined using a rapid-filtration assay.

2. Both MTHF and folic acid were taken up by membrane vesicles at 25° and enterocytes at 37° by a pH-dependent mechanism with maximum uptake when the pH of the incubation medium was 5·0.

3. Experiments in which the osmotic pressure of the medium was raised in successive increments with the non-absorbable sugar cellobiose indicated that transport rather than membrane binding was the main component of uptake.

4. Experiments at pH 5·0 showed that uptake of MTHF and folic acid was saturable and that the characteristics of folate transport were similar in both tissue preparations: (a) transport rates of both MTHF and folic acid were constant during the first 1-2 min for a given folate concentration, then declined to reach a steady-state in 10-30 min; (b) initial velocities of transport of MTHF and folic acid increased in proportion to their concentrations up to 7-10 μM, but the rate of increase slowed thereafter until saturation was reached at 20-25 μM (Km for brushborder-membrane vesicles 40·8 and 62·9 μM, Km for enterocytes 50·9 and 55·2 μM for MTHF and folic acid respectively). Values of Vmax for membrane vesicles (pmol/mg protein per min) were 46·5 MTHF or 40·3 folic acid; enterocytes Vmax (pmol/107 cells per min) 15·9 MTHF or 30·6 folic acid; (c) uptake of MTHF and folic acid by brush-border-membrane vesicles and enterocytes measured under steady-state conditions approached saturation at 50 μM for each analogue (Km for membrane vesicles 58·1 and 55·2 μM, Km for enterocytes 43·1 and 49·4 μM for MTHF and folic acid respectively; Vmax for membrane vesicles 49·7 and 77·8 pmol/mg protein, for enterocytes 52·8 and 54·7 pmol/107 cells for MTHF and folic acid respectively).

5. It was concluded that transport of MTHF and folic acid was by a similar pH-dependent mechanism both in brush-border-membrane vesicles and in intact enterocytes. At pH 5·0, transport involved a saturable carrier-mediated process located in the brush-border membrane.

Type
Research Article
Information
British Journal of Nutrition , Volume 59 , Issue 3 , May 1988 , pp. 485 - 495
Copyright
Copyright © The Nutrition Society 1988

References

Bensadoun, A. & Weinstein, D. (1976). Analytical Biochemistry 70, 241–250.CrossRefGoogle Scholar
Blair, J. A. & Matty, A. J. (1974). Clinics in Gastroenterology 3, 183–197.CrossRefGoogle Scholar
Blakeborough, P. & Salter, D. N. (1985). Abstracts of the XIII International Congress of Nutrition, Brighton, p. 149.Google Scholar
Booth, A. G. & Kenny, A. J. (1974). Biochemical Journal 142, 575–581.CrossRefGoogle Scholar
Colman, N., Hettiarachchy, N. & Herbert, V. (1981). Science 211, 1427–1429.CrossRefGoogle Scholar
Eilam, Y., Ariel, M., Jablonska, M. & Grossowicz, N. (1981). American Journal of Physiology 240, G170–G175.Google Scholar
Elsborg, L. (1974). Danish Medical Bulletin 21, 1–11.Google Scholar
Ferland, S. & Hugon, J. S. (1979). In Vitro 15, 288–293.CrossRefGoogle Scholar
Ford, W. L. (1979). In Handbook of Experimental Immunology, vol. 2, Cellular Immunology, pp. 23.10–23.22 [Weir, D. M. editor]. Oxford: Blackwell.Google Scholar
Hopfer, U., Nelson, K., Perrotto, J. & Isselbacher, K. I. (1973). Journal of Biological Chemistry 248, 25–32.CrossRefGoogle Scholar
Lee, S.-K., Singh, J. & Taylor, R. B. (1975). European Journal of Immunology 5, 259–262.CrossRefGoogle Scholar
Lucas, M. L. & Blair, J. A. (1978). Proceedings of the Royal Society of London. Series A 200, 27–41.Google Scholar
Moyer, M. P. (1983). Proceedings of the Society for Experimental Biology and Medicine 174, 12–15.CrossRefGoogle Scholar
Murer, H., Ammann, E., Biber, J. & Hopfer, U. (1976). Biochimica et Biophysica Acta 433, 509–519.CrossRefGoogle Scholar
Parks, D. R., Bryan, V. M., Oi, V. T. & Herzenberg, L. A. (1979). Proceedings of the National Academy of Sciences, USA 76, 1962–1966.CrossRefGoogle Scholar
Selhub, J., Gay, A. C. & Rosenberg, I. H. (1979). In The Chemistry and Biology of the Pteridines, pp. 593–596 [Kisliuk, R. and Brown, G. M. editors]. Amsterdam: Elsevier/ North Holland Press.Google Scholar
Selhub, J. & Rosenberg, I. H. (1981). Journal of Biological Chemistry 256, 4489–4493.CrossRefGoogle Scholar
Strum, W. B. (1979). Biochimica et Biophysica Acta 554, 249–257.CrossRefGoogle Scholar
Watford, M., Lund, P.& Krebs, H. A. (1979). Biochemical Journal 178, 589–596.CrossRefGoogle Scholar