EFFECT OF SERUM-FREE MEDIUM ON CYTOCHROME P450-DEPENDENT METABOLISM AND TOXICITY IN RAT CULTURED-HEPATOCYTES

Cytochrome P450 (P450)-dependent activities in homogenates of rat hepatocytes cultured for 96 hr in serum-free and serum-containing medium were compared. Benzphetamine and erythromycin N-demethylases, 7-methoxy- and propoxy-coumarin O-dealkylases, p-nitrophenol hydroxylase and 7-ethoxy- and pentoxy-resorufin O-dealkylases were all maintained at higher levels in hepatocytes cultured in serum-free medium, although there was some selectivity with respect to the extent of the maintenance relative to the activities in fresh cells. The toxicities of coumarin, precocene I and precocene II to 24 hr hepatocyte cultures, determined as decreased survival, were also shown to be increased in serum-free medium. However, the magnitude of the difference between media with respect to the toxicity of precocene II was decreased in hepatocytes cultured for 72 hr. The observed increase in toxicity is consistent with the improved maintenance of P450 in hepatocytes cultured in serum-free medium, although there is still a selective decline in P450 activities and toxicity with increased time in culture. The activity of alcohol dehydrogenase and the toxicity of allyl alcohol were similar in hepatocytes cultured in serum-free and serum-containing medium for 96 hr. The absence of serum did not affect the non-protein sulphydryl content of the cultures.