Benzo(a)pyrene metabolism in the isolated perfused mouse lung

A method is described for preparing and maintaining an isolated perfused and ventilated mouse lung. The preparation is especially suited for studying xenobiotic metabolism or toxicological interactions, in a species with a broad spectrum of studies in pulmonary toxicology. The preparation is viable with respect to drug metabolism for up to two hours, as judged from studies of aniline oxidation to p-aminophenol. With [14C]-benzo(a)pyrene as substrate for the lungs of male ICR Swiss mice, the major ethyl acetate-extractable metabolites are the 3-hydroxy, 9,10-dihydrodiol, 7,8-dihydrodiol, and 4,5-dihydrodiol derivatives. The rates of individual BaP metabolite production are increased in lungs from mice pretreated with Aroclor 1254 or beta-naphthoflavone, substances known to induce increased synthesis of cytochrome P-450. Small amounts of water-soluble BaP metabolites were hydrolyzed by beta-glucuronidase and aryl sulfatase, suggesting the presence of enzymes required for these conjugations. These results support the existence of significant cytochrome P-450-dependent and conjugative BaP metabolism in the intact mouse lung, similar to that examined in other species, and capable of contributing to the systemic metabolism of this carcinogen.