Na+ + Cl−‐gradient‐driven, high‐affinity, uphill transport of taurine in human placental brush‐border membrane vesicles

Abstract

Uptake of taurine in human placental brush-border membrane vesicles was greatly stimulated in the presence of an inwardly-directed Na⁺ + Cl⁻-gradient and uphill transport of taurine could be demonstrated under these conditions. Na⁺ as well as Cl⁻ were obligatory for this uptake and both ion gradients could energize the uphill transport. This Na⁺ + Cl⁻-gradient-dependent taurine uptake was stimulated by an inside-negative membrane potential, demonstrating the electrogenicity of the process. The uptake system was highly specific for β-amino acids and the K _m of the system for taurine was 6.5 ± 0.4 μM.