Low levels of expression of cytochromes P-450 in normal and cancerous fetal pancreatic tissues of hamsters treated with NNK and/or ethanol

Previous studies from this laboratory have demonstrated that administration of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1- butanone (NNK) to pregnant hamsters results in tumors in the offspring. Whe reas treatment with NNK alone caused mainly tumors in the respiratory tract of the treated offspring, cotreatment with ethanol (EtOH) and NNK shifted the site of tumor formation to the pancreas. In order to determine potentia l mechanisms for the cocarcinogenic effects of EtOH, the levels of NNK meta bolites and expression of various CYPs implicated in the metabolic activati on of NNK were determined in fetal liver and pancreas. NNK and its metaboli te, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), were detected at low and variable levels in the fetal liver and pancreas, with an NNAL to NN K ratio greater than 20 in both organs. EtOH had no effect on the amount of metabolites found in either organ, Results obtained with the fetal liver s amples, which served as a positive control, correlated very well with our p revious studies demonstrating low levels of expression of several CYP isozy mes at both the protein and RNA level. Western blot analysis showed low but detectable levels of CYP1A1, barely detectable levels of CYP2E1, and an ab sence of CYP1A2 and 2B family members in the fetal pancreas. RNA transcript s were undetectable by ribonuclease protection in the fetal pancreas, altho ugh readily seen in fetal liver samples. Treatment with NNK, EtOH, or both NNK and EtOH had small and variable effects on the levels of metabolism of NNK and expression of the isozymes, These findings suggest that alternative mechanisms may be responsible for transplacentally induced tumors in this model system.