title: Ionic requirements for taurocholate transport in rat liver plasma membrane vesicles.
abstract: As part of the enterohepatic circulation, taurocholate is taken up by hepatocytes by a Na+-gradient-dependent, carrier-mediated process. The dependence of taurocholate uptake on the presence of a Na+ gradient, outside greater than inside, has been studied in isolated rat liver plasma membranes. The uptake is specific for sodium, and a cotransport stoichiometry of 2 Na+ per taurocholate taken up was found. The presence of K+ ions inside the vesicles was also found to be essential for maximum Na+-stimulated uptake of taurocholate, although a K+ gradient is not required. Mg2+ was almost as effective as K+ in this regard. The symport of Na+ and taurocholate during uptake was shown to be electrogenic, so that K+ may act as an exchange counterion preventing the accumulation of positive charge within the vesicles.
mesh_terms: D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002413:Cations, Divalent; D002414:Cations, Monovalent; D002462:Cell Membrane / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008564:Membrane Potentials; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000378:metabolism; D013656:Taurocholic Acid / Q000378:metabolism*
chemical_list: D002413:Cations, Divalent; D002414:Cations, Monovalent; D013656:Taurocholic Acid; D011189:Potassium Chloride; D012964:Sodium