Metabolism of 1-nitropyrene in mice: transport across the placenta and mammary tissues.

The distribution and metabolism of the environmental pollutant 1-nitropyrene was studied in C57B1/6N mice following oral or intraperitoneal dosing. When administered by gavage, 1-nitropyrene and its metabolites demonstrated biphasic elimination kinetics from the blood, with half-lives of 0.3 and 1.8 days and a distribution volume of 74 ml. Intraperitoneal administration resulted in similar biphasic elimination, with half-lives of 0.5 and 3 days and a distribution volume of 98 ml. Treating pregnant C57B1/6N (C3H sire) mice by gavage resulted in similar absorption and elimination kinetics of 1-nitropyrene and metabolites, except that the distribution volume increased to 123 ml. 1-Nitropyrene and/or its metabolites (0.7% of the administered dose) crossed the placenta and accumulated in the fetuses and amniotic fluid, with both C-oxidized and nitroreduced metabolites being detected. Suckling neonates accumulated 1-nitropyrene and its metabolites when their dams were administered 1-nitropyrene by gavage. Each neonate received approximately 0.1% of the administered dose and demonstrated the presence of both C-oxidized and nitroreduced metabolites. These results demonstrate that this environmental pollutant is capable of crossing the placenta or mammary tissues to expose the offspring to a potentially genotoxic compound.