In 1993, the US Environmental Protection Agency (U.S. EPA, 1993) established a cancer risk for N-nitrosodimethylamine (NDMA) of about two orders of magnitude higher than the risk estimate by Health Canada (0.7 ng/kg bodyweight per day) ( Health Canada,

2002), while the rat carcinogenic potency of N-nitrosodiethylamine (NDEA) is about three times that of NDMA ( Lijinsky, 1992). In humans, the average intake of NDEA from food is approximately 1 μg/day ( Scanlan, 1983). However, NDEA is also found in cigarettes and cigarette smoke at 0.0083–0.0405 μg/cigarette, as well as in rolls, buns, muffins and bagels (0.023 μg/100 g), ham (0.149 μg/100 g) and even oysters (0.109 μg/100 g) Ribociclib mw ( Stuff et al., 2009). Thus, it is difficult to predict the exact exposure rate of individuals.

NDEA TGF-beta family is a carcinogen that can induce tumors in a variety of organs of many animal species (Magee and Barnes, 1956, Peto et al., 1991 and Lijinsky, 1992). It requires metabolic activation through P450-catalyzed β-hydroxylation, generating unstable metabolites that alkylate the DNA and thus cause tumor formation (Ribeiro Pinto, 2000). Due to their high expression levels of cytochrome P450 (CYP), hepatocytes represent the most suitable model to investigate CYP induction in relation to drug metabolism. In fact it has been shown that phenobarbital (PB) induces markedly increased expression of several phase I and II enzymes, including several forms of cytochrome P450 (Gonzales, 1989 and Waxman and Azaroff, 1992). In the present work we focused on CYP2B1 and CYP2B2, which are two of the major P450 cytochromes that are induced by PB in rat livers. We correlated N-nitrosodiethylamine genotoxicity (micronuclei and mitotic index) and cytotoxicity (survival,

apoptosis, and necroses rates) in primary cultures of female rat hepatocytes in the presence of PB. Female albino Fischer 344 rats (F-344/DuCrl) of 6–8 weeks of age were used Phosphoribosylglycinamide formyltransferase for the experiments (Charles River Laboratories, Germany). The light/dark regime was 12/12 h, and standard pelleted rat feed and drinking water was supplied ad libitum. Three female Fischer 344 rat livers were used per NDEA concentration. Nitrosamines are able to induce liver tumors not only in male, but also in female rats (Lijinsky, 1992). The study was conducted in compliance with the National Research Council of Austria’s “Guide for the Care and Use of Laboratory Animals”. Hepatocytes were prepared according to the two-step collagenase perfusion method (Eckl and Riegler, 1997). Rats were anesthetized with 200 mg/kg sodium pentobarbital. Following hepatic portal vein cannulation, the livers were perfused for 15 min at a flow rate of 15 mL/min with solution A (142 mM NaCl, 6.7 mM KCl, 10 mM HEPES, pH 7.4). Subsequently, the livers were perfused for 20 min (flow rate 10 mL/min) using 200 mL solution C (buffer A and 5.7 mM CaCl2 at a ratio of 9:1) containing 0.