On the mechanism of sugar and amino acid interaction in intestinal transport.
The influence of amino acids on D-glucose transport was studied in isolated vesicles of brush border membrane from rat small intestine. It is demonstrated that: (a) Uptake of D-glucose by the membranes is inhibited by simultaneous flow of L- and D-alanine into the vesicles. (b) Addition of L-alanine to membranes pre-equilibrated with D-glucose causes efflux of this sugar. (c) The influence of amino acids on D-glucose is dependent on the presence of Na+. (d) The ionophorous agents monactin and valinomycin are able to prevent the transport interaction of D-glucose and amino acids. Monactin is effective in the presence of Na+ without further addition of other cations, while valinomycin is effective only with added K+, in accordance with the known specificity of these antibiotics. (e) The inhibitory effect increases with L-alanine concentration up to about 50 mM after which it levels off. The experiments provide evident that the Na+-dependent sugar and amino acid fluxes across the brush border membrane are coupled electrically.
D000409:Alanine / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001693:Biological Transport, Active; D005947:Glucose / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism*; D007421:Intestine, Small / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008353:Mannitol / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000494:pharmacology; D014634:Valinomycin / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D014634:Valinomycin; D008353:Mannitol; D012964:Sodium; D005947:Glucose; D000409:Alanine; D011188:Potassium