N-Nitrosodiethylamine genotoxicity in primary rat hepatocytes: effects of cytochrome P450 induction by phenobarbital.

Primary hepatocytes are widely used in investigating drug metabolism and its toxicological effects. N-Nitrosodiethylamine (NDEA)-induced genotoxicity and cytotoxicity was used in primary cultures of female rat hepatocytes in the presence of phenobarbital (PB). PB pre-treatment (1mM) increased the number of necrotic (2-fold) and apoptotic cells (4-fold) after NDEA treatment (0.21-105 μg/mL). The mitotic indices and the number of micronucleated cells decreased, thus suggesting cytotoxicity. An increased number of chromosomal aberrations were observed after pre-treatment with PB. NDEA-treatment (0.21-21 μg/mL) induced expression of the CYP2B1 and CYP2B2 mRNA and PB treatment alone induced ~6-fold and ~2-fold increases of CYP2B1 and CYP2B2 mRNA, respectively. NDEA treatment following PB exposure increased CYP2B1 mRNA expression under all tested concentrations and also increased CYP2B2 expression at 21 and 105 μg/mL. Our data suggest that the alteration of CYP2B1/2 expression by PB increased the cytotoxicity and genotoxicity of NDEA leading to the final genotoxic metabolite.