Vitamin D-Dependent Phosphate Transport by Chick Intestine: Inhibition by Low Na+ and N-Ethylmaleimide
In vitamin D-deficient chicks the duodenum displays a high capacity of phosphate (Pi) transfer from lumen to blood side, while jejunum and ileum show only low rates of transepithelial Pi transport. Vitamin D3 stimulates intestinal phosphate absorption in all parts of the chick small intestine: The increment in Pi absorption due to vitamin D3 is relatively small in the duodenum and also in the ileum. However, in the jejunum the vitamin increases the rate of Pi transfer to a level comparable to that displayed by the duodenum. In the jejunum, entry of Pi from the lumen is by a carrier-mediated energy-dependent transport mechanism presumably located at the brush border. Vitamin D3 enhances the maximal velocity of this process two- to threefold. This effect is probably due to the action of the active metabolite, 1,25-dihydroxy-vitamin D3 The exact mechanism by which the latter stimulates Pi influx is not known at present. However, a protein syntietic step seems to be necessary for enhancement of Pi absorption by the hormonally acting sterol (1, 2, 3).
KeywordsPhosphate Transport Absorptive Process Mucosal Solution Intestinal Phosphate Absorption Mucosal Border
Unable to display preview. Download preview PDF.
- 1.Peterlik, M., and Wasserman, R.H.: Basic features of the vitamin D-dependent phosphate transport by chick jejunum in vitro. Fed. Proc. 34: 887, 1975Google Scholar
- 2.Peterlik, M., and Wasserman, R.H.: Control of intestinal phosphate absorption by vitamin D. Isr. J. Med. Sci 12: 1492, 1976Google Scholar
- 3.Peterlik, M., and Wasserman, R.H.: Effect of vitamin D and 1,25-dihydroxyvitamin D on intestinal trans-part of phosphate. In: Phosphate Metabolism (ed. by Massry, S.G., and Ritz, E. ), p. 323, Plenum Press, New York 1977Google Scholar
- 5.Wasserman, R.H., and Corradino, R.A.: Vitamin D, Calcium and Protein Synthesis. In: Vitamins and Hormones 31:43, Academic Press, New York 1973Google Scholar
- 7.Fiske, C.H., and SubbaRow, Y.: The colorimetric determination of phosphorus. J. Biol. Chem. 66: 375, 1925Google Scholar
- 11.Kinne, R., Berner, W., Hoffmann, N., and Murer, H.: Phosphate Transport by Isolated Renal and Intestinal Plasma Membranes. In: Phosphate Metabolism (ed. by Massry, S.G., and Ritz, E. ), p. 265, Plenum Press, New York 1977Google Scholar
- 12.Peterlik, M.: Effects of Vitamin D on Phosphate Transport by Embryonic Chick Duodeíium. Abstr. 6th Int. Conf. Endocrinology, London, July 1977Google Scholar