A COMPARISON OF HEPATIC ENZYME-ACTIVITIES AND THEIR MODULATION BY DEXAMETHAZONE IN FRESHLY ISOLATED AND CULTURED-HEPATOCYTES AND IN THE DIFFERENTIATED HEPATOMA-CELL LINE, 2SFOU

Rodent hepatocytes are mitotically inhibited and lose hepatospecific f unctions over time in culture. In contrast, some differentiated hepato ma cell lines express stable hepatospecific functions in culture, but at much lower levels than those initially found in primary hepatocytes . A number of hepatospecific functions were measured in freshly isolat ed and cultured rat hepatocytes; these were compared to activities fou nd in the differentiated Reuber hepatoma cell line, 2sFou. The effects of dexamethazone on these activities were also investigated, since de xamethazone is reported to enhance the expression of organotypic funct ions. The P450-related activities (ethoxyresorufin-O-deethylase activi ty and pentoxyresorufin-O-depentylase activity) and glucose-6-phosphat ase activity declined in hepatocytes with increasing time in culture. The same activities in 2sFou cells were similar to those in hepatocyte s which had been cultured for 72 hours. Tyrosine amino transferase (TA T) activity declined in hepatocyte cultures with time, but dexamethazo ne (1 mu M) restored activity up to freshly isolated cell values. TAT activity in hepatoma cells exceeded that in hepatocytes and was highly inducible by dexamethazone. gamma-Glutamyl transpeptidase activity in creased with culture time in hepatocytes and was also highly expressed in 2sFou cells. In hepatocytes, the activity of a high affinity alcoh ol dehydrogenase (ADH) declined with time in culture. In 2sFou cells, there was evidence of a low affinity (extra-hepatic or fetal) form of ADH, which was not evident in cultured hepatocytes.