Transport ofl-cysteine by rat renal brush border membrane vesicles

Abstract

Summary Brush border membranes were isolated from rat renal cortex by a divalent cation precipitation method.l-³⁵S-cysteine uptake into the vesicles was measured by a rapid filtration method. Only minimal binding of the amino acid to the vesicles was observed. Sodium stimulatesl-cysteine uptake specifically. Anion replacement experiments, experiments in the presence of potassium/valinomycin-induced diffusion potential as well as experiments with a potential-sensitive fluorescent dye document an electrogenic sodium-dependent uptake mechanism forl-cysteine. Tracer replacement experiments as well as the fluorescence experiments indicate a preferential transport ofl-cysteine. Transport ofl-cysteine is inhibited byl-alanine andl-phenylalanine but not byl-glutamic acid and thel-basic amino acids. Initial, linear influx kinetics provide evidence for the existence of two transport sites. The results suggest (a) sodium-dependent mechanism(s) forl-cysteine shared by other neutral amino acids.