Abstract
1. The effect of the addition of amino acids to the intestinal lumen upon the movement of the monosaccharide alpha-methyl-D-glucopyranoside (alpha MG) from the preloaded epithelium into the blood and into the lumen of the vascularly perfused frog small intestine has been studied. 2. The neutral hydrophobic amino acids tryptophan, leucine, phenylalanine, tyrosine, isoleucine, valine, norleucine and cycloleucine all rapidly inhibit the exit of alpha MG out of the epithelium into the vascular bed. They stimulate backflux of the sugar from the epithelium into the lumen to a very much smaller extent. 3. L-Leucine is a more effective inhibitor of alpha MG exit into the blood than is D-leucine. Near-maximal inhibition of alpha MG exit is seen with 10 mM-L-leucine in the intestinal lumen. 4. The addition of leucine (10 mM) to the lumen of the intestine preloaded with alpha MG approximately halves the rate constant for alpha MG washout into the blood from 12.6 +/- 1.7 (4) x 10(-3) to 5.5 +/- 1.4 (4) x 10(-3) min-1, without appreciably altering the pool of monosaccharide in the tissue. The inhibitory effect of L-leucine upon alpha MG exit into the blood is not abolished by the presence of phlorizin (5 x 10(-5) M) in the intestinal lumen. 5. The complex pattern of inhibition of alpha MG transfer from the lumen to the blood observed upon the addition of L-leucine to the lumen is consistent with the finding that the amino acid inhibits the exit of the monosaccharide out of the epithelium into the blood in addition to any inhibitory effect upon sugar entry across the brush border. 6. It is suggested that alpha MG may be a substrate for a proposed transport system for neutral hydrophobic amino acids which, it is suggested, is present in the basolateral membrane of the epithelial cell.
Full text
PDF
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Boyd C. A. Amino acid inhibition of the exit of monosaccharide from the intestinal epithelium [proceedings]. J Physiol. 1977 Oct;271(2):48P–49P. [PubMed] [Google Scholar]
- Boyd C. A., Cheeseman C. I., Parsons D. S. Amino acid movements across the wall of anuran small intestine perfused through the vascular bed. J Physiol. 1975 Sep;250(2):409–429. doi: 10.1113/jphysiol.1975.sp011062. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Boyd C. A. Classification of systems available for amino acid exit from small intestine into the blood [proceedings]. J Physiol. 1978 Mar;276:52P–53P. [PubMed] [Google Scholar]
- Boyd C. A., Parsons D. S. Movements of monosaccharides between blood and tissues of vascularly perfused small intestine. J Physiol. 1979 Feb;287:371–391. doi: 10.1113/jphysiol.1979.sp012665. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Bronk J. R., Leese H. J. Accumulation of amino acids and glucose by the mammalian small intestine. Symp Soc Exp Biol. 1974;(28):283–304. [PubMed] [Google Scholar]
- Murer H., Sigrist-Nelson K., Hopfer U. On the mechanism of sugar and amino acid interaction in intestinal transport. J Biol Chem. 1975 Sep 25;250(18):7392–7396. [PubMed] [Google Scholar]
- NEWEY H., SMYTH D. H. EFFECTS OF SUGARS ON INTESTINAL TRANSFER OF AMINO-ACIDS. Nature. 1964 Apr 25;202:400–401. doi: 10.1038/202400b0. [DOI] [PubMed] [Google Scholar]
- Reiser S., Hallfrisch J. Stimulation of neutral amino acid transport by fructose in epithelial cells isolated from rat intestine. J Nutr. 1977 May;107(5):767–774. doi: 10.1093/jn/107.5.767. [DOI] [PubMed] [Google Scholar]
- Ullrich K. J. Sodium-dependent transport processes in the renal proximal tubule [proceedings]. J Physiol. 1978 Dec;285:10P–11P. [PubMed] [Google Scholar]