Excretion of taurocholate from isolated hepatocytes.

Efflux of taurocholate from isolated rat hepatocytes was studied to characterize the mechanism of bile acid secretion. Cells were incubated with taurocholate for 15 min. The amount of the intracellularly accumulated bile acid was directly related to the concentration in the medium. Transfer of the loaded cells from the incubation medium to a medium without taurocholate led to taurocholate efflux. Efflux was saturable, its activation energy amounted to 12 kcal/mol (50 kJ). It was strongly inhibited by the metabolic inhibitor antimycin A and to a lesser extend by the uncoupler carbonylcyanide-m-chlorophenylhydrazone. Dinitrofluorobenzene and mersalyl, reagents which react with amino acids, inhibited efflux by about 30% when applied at concentrations of 50 muM. Ouabain increased the rate of efflux. The observations indicate that secretory functions are maintained in isolated liver cells.