Measurement of unscheduled DNA synthesis by aflatoxin B1in primary culture of hepatocytes from rats pretreated with phenobarbital and 3-methylcholanthrene in vivo

Abstract

The inducibility of cytochrome P-450 associated monooxygenase was studied in primary cultures of ault rat hepatocytes. Rats were pretreated with phenobarbital (PB) or 3-methylcholanthrene (3-MC) and hepatocytes were isolated from PB-, 3-MC-treated, and untreated rats by collagenase perfusion technique. At the initial time of isolation, 3-MC enhanced 7-ethoxycoumarine-0-deethylase, Aryl hydrocarbon hydroxylase and biphenyl-4-hydroxylase by a factor of 12,60 and 2.5, except for aminopyrine-N-demethylase, respectively. The activities of enzymes were maintained higher level until 72 hrs when compared to untreated groups. Phenobarbital-pretreatment showed similar inducibility, but the magnitutes in induced enzymes level were relatively low compared to those by 3-MC. To conform the enhanced effects of metabolizing capability, unscheduled DNA synthesis (UDS) by Aflatoxin $B_1 (AF-B_1)$ was measured 24 hr after isolation of hepatocytes. UDS induced by $AF-B_1$ was slightly increased in PB-pretreated hepatocytes while decreased at low dose of $AF-B_1$ in 3-MC-pretreated hepatocytes compared to that in naive hepatocytes. These results suggest that the metabolizing capability of primary cultures of hepatocytes is increased by pretreatment of rats with PB or 3-MC.