Immortalization of rat hepatocytes by fusion with hepatoma cells. II. Studies on the transport and synthesis of bile acids in hepatocytoma (HPCT) cells.

ABSTRACT

Hepatocytoma (HPCT) cells were screened for the uptake of bile acids, the organic anion bumetanide and phalloidin. In addition, the rate of bile acid synthesis and the ability to conjugate exogenously added free bile acids was investigated. The unconjugated bile acid cholate is transported via carrier-mediated uptake into HPCT cells of the clone 1E3. This transport is expressed less by HPCT clones 1F9 and 2E9. Cholate uptake is 40% sodium-dependent, temperature-sensitive, and reveals a km-value of 47 +/- 9 pmol/l and a Vmax-value of 94 +/- 29 pmol x min-1 x mg-1. However, all of the HPCT clones lack carrier-mediated uptake of glycocholate and taurocholate. The clones which possess cholate transport are sensitive to phalloidin and take up bumetanide. In higher cell passages cholate transport and the sensitivity to phalloidin are reduced. This process is not prevented by a selection procedure with HAT-medium, nor is it stimulated by nicotinamide, dimethyl sulfoxide, or sodium butyrate. The cells of the 1E3, 1F9 and 2E9 clones, but not Fao hepatoma cells synthesize bile acids endogenously even after 60 passages, and conjugate exogenously added cholate with taurine and glycine. These results indicate that liver-specific properties of freshly isolated hepatocytes which are lacking in the parental hepatoma cells are maintained in HPCT cells.