Betaine transport in rabbit renal brush-border membrane vesicles

Organic osmolyte betaine transport was observed and studied in rabbit renal brush-border membrane vesicles (BBMV). Na+ betaine and H+-betaine transport is electrogenic in character, as concentrative induction was observed only during occurrence of membrane potential. Chloride presence in the medium had no influence on betaine. L-protine antagonized Na+- and H+- betaine transport, and the H+- sensitive betaine pathway alone was inhibited by glycine. The highest rate of net betaine transport (Jmax) was enhanced by the simultaneous presence of Na+ and H+ gradients. Two unique betaine transport pathways in BBMV were identified. These pathways are defined by their Na+ or H+ sensitivity and their proline and glycine specificity.