Hepatic taurine transport: A Na+-dependent carrier on the basolateral plasma membrane

J. C. Bucuvalas, A. L. Goodrich, F. J. Suchy

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24 Scopus citations

Abstract

Highly purified rat basolateral liver plasma membrane vesicles were used to examine the mechanism and the driving forces for hepatic uptake of the β-amino acid, taurine. An inwardly directed 100 mM NaCl gradient stimulated the initial rate of taurine uptake and energized a transient twofold accumulation of taurine above equilibrium ('overshoot'). In contrast, uptake was slower and no overshoot was detected in the presence of a KCl gradient. A negative intravesicular electrical potential generated by the presence of permeant anions or an outwardly directed K+ gradient with valinomycin increased Na+-stimulated taurine uptake. External Cl- stimulated Na+-dependent tuarine uptake independent of effects on the transmembrane electrical potential difference. Na+-dependent taurine uptake showed a sigmoidal dependence on extravesicular Na+ concentration, suggesting multiple Na+ ions are involved in the translocation of each taurine molecule. Na+-dependent taurine uptake demonstrated Michaelis-Menten kinetics with a maximum velocity of 0.537 nmol·mg protein-1·min-1 and an apparent K(m) of 174 μM [3H]taurine uptake was inhibited by the presence of excess unlabeled taurine, β-alanine, or hypotaurine but not by L-glutamine or L-alanine. In summary, using basolateral liver plasma membrane vesicles, we have shown that hepatic uptake of taurine occurs by a carrier-mediated, secondary active transport process specific for β-amino acids. Uptake is electrogenic, stimulated by external Cl-, and requires multiple Na+ ions for the translocation of each taurine molecule.

Original languageEnglish
Pages (from-to)16/3
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume253
Issue number3
StatePublished - 1987
Externally publishedYes

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