Kinetics and specificity of L-alanine transport across the basolateral cell surface in isolated oxyntic glands.
The time course, kinetics, specificity and sodium-dependence of alanine uptake by isolated oxyntic glands were studied. The uptake of alanine by the hydrolyzed cells was measured directly, after incubation of the glands with L-[3H]alanine. L-Alanine total influx was saturable and apparently mediated by a single entry system (Kt = 7.93 mM and Vmax = 8.0 mumol.mg-1.30s-1). The Kt was comparable to previously reported values for L-alanine transport in other epithelial cells. Kinetic studies performed in the presence and absence of Na+ suggest L-alanine uptake is mainly mediated by a Na(+)-dependent carrier system, but in addition, a minor diffusional component has been detected. Cross inhibition experiments performed over a wide range of concentrations (1 to 100 mM) suggest that the Na(+)-dependent transport system for alanine resembles system A and displays higher affinity for L-serine (Ki = 1.81 mM) than for L-alanine (K't = 4.86 mM); a lower affinity was found for L-cysteine (Ki = 16.30 mM). Results obtained with MeAIB support the hypothesis that system A is present at the basolateral membrane of the gland cells.
Bravo
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Department of Physiological Sciences, Faculty of Biological Sciences and Natural Resources, University of Concepción, Chile.
Sobrevía
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D000409:Alanine / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D007700:Kinetics; D010295:Parietal Cells, Gastric / Q000378:metabolism*; D011817:Rabbits
D000409:Alanine