Uptake of Taurocholic Acid into Isolated Rat‐Liver Cells

Leslie R. SCHWARZ, Reinhold BURR, Michael SCHWENK, Erich PFAFF, Helmut GREIM

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239 Scopus citations

Abstract

Binding and transport characteristics for uptake of taurocholic acid by isolated rat liver cells were studied. An adsorption of taurocholate to the cell surface is terminated in less than 15 s. A Ks of 0.55 mM and a total binding capacity of 3.8 nmol/mg cell protein is determined. The rate of uptake of taurocholate follows Michaelis‐Menten kinetics with Km= 19 μM and V= 1.7 nmol/mg protein min. There is a broad pH optimum for uptake between pH 6.5–8.0. The activation energy amounts to 29 kcal/mol. At high taurocholate concentration an unusual upward bend is observed in the Arrhenius plot. Taurocholate uptake is competitively inhibited by taurochenodeoxycholate (Ki= 9 μM). It is noncompetitively inhibited by bromosulfophthalein (Ki= 3 μM). At physiological taurocholate concentrations a 200‐fold intracellular accumulation of taurocholate is observed. Uptake is inhibited by about 75% by either antimycin A, carbonylcyanide m‐chlorophenyl‐hydrazone, ouabain. Replacement of extracellular Na+ by either K+ or sucrose results in a 75% decrease of uptake. It is concluded that taurocholate uptake is a carrier‐mediated process, and suggested that the energy for intracellular accumulation is made available by cotransport of Na+.

Original languageEnglish
Pages (from-to)617-623
Number of pages7
JournalEuropean Journal of Biochemistry
Volume55
Issue number3
DOIs
StatePublished - Jul 1975
Externally publishedYes

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