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Na+ + Cl- -gradient-driven, high-affinity, uphill transport of taurine in human placental brush-border membrane
Y Miyamoto1, D F Balkovetz, F H Leibach
1Department of Cell and Molecular Biology, Medical College of Georgia, Augusta 30912-2100.
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 beta-amino acids and the Km of the system for taurine was 6.5 +/- 0.4 microM.