Ethanol inhibits Na+-gradient-dependent uptake of L-amino acids into intestinal brush border membrane vesicles

Brush border membrane vesicles from hamster jejunum were used to investigate the effects of ethanol on Na+-dependent transport of amino acids. Imposition of an inwardly directed gradient of NaCl resulted in transient accumulation of L-alanine and L-phenylalanine, followed by a gradual decline to equilibrium levels. Ethanol reduced both the rate of uptake and the maximum accumulation of these amino acids without altering the final equilibrium level. The inhibitory effects of ethanol on L-alanine uptake were dose dependent and reversible. On the other hand, ethanol had no effect on the rate of uptake of L-alanine or the final equilibrium level attained when vesicles were incubated with a KCl gradient or when NaCl was equilibrated across the vesicle membrane. These results suggest that ethanol does not inhibit Na+-dependent uptake of neutral amino acids by direct inhibition of the Na+-dependent transport systems for these solutes.