Effects of gemfribozil and clofibric acid on the uptake of taurocholate by isolated rat hepatocytes

Abstract

Clinical use of fibrate hypolipidaemic agents has been associated with an increased incidence of hepatobiliary dysfunction including increased bile lithogenicity, gallstone formation, and cholestasis. The hepatic transport of bile acids plays an important role in bile formation and flow, and interference with the hepatocellular transport of bile acids may result in hepatobiliary dysfunction. The aim of this study was to investigate the effects of gemfibrozil and clofibric acid on the uptake of taurocholate by rat isolated hepatocytes. In control hepatocyte preparations (N = 5) at 37 degrees, the uptake of taurocholate was described by saturable Michaelis-Menten kinetics with a mean (+/-SD) Km of 44.1 +/- 10.2 microM and Vmax of 62.0 +/- 23.0 nmol/10(6) cells/min. In the presence of 200 microM clofibric acid, there was no significant change in the kinetics of taurocholate uptake. However, in the presence of 200 microM gemfibrozil there was a statistically significant (P < 0.05) decrease in the Vmax of taurocholate uptake (32.0 +/- 18.2 nmol/10(6) cells/min, N = 5) and no change (P > 0.05) in Km (48.5 +/- 29.5 microM, N = 5). Gemfibrozil behaved as a non-competitive inhibitor of taurocholate uptake, with a Ki of 144 microM, which is approximately 50 times higher than the unbound gemfibrozil concentrations achieved clinically in humans. Thus, gemfibrozil and clofibric acid did not appear to directly alter the hepatic uptake of taurocholate at clinically relevant concentrations.