The metabolism of benzo(alpha)pyrene by cytochrome P-450 in transformable and nontransformable C3H mouse fibroblasts.

Abstract

The microsomal metabolism of benzo(a)pyrene and its enhancement by inducers of aryl hywdrocarbon hydroxylase were studied in three C3H mouse fibroblast cell lines and in C3H mouse liver and lung. The cell lines examined included C3H/10T 1/2 CL8, a line that can be transformed by treatment with benzo(a)pyrene; CVP3SC6, a line which cannot be transformed by treatment with benzo(a)pyrene; and C3H/10T 1/2 CL16, a transformed cell line derived from 3-methylcholanthrene-treated C3H/10T 1/2 CL8 cells. Of four polycyclic hydrocarbons examined, benz(a)anthracene was found to be the most effective inducer of aryl hydrocarbon hydroxylase activity, while 3-methylcholanthrene did not induce. The extent of this induction in all three cell lines was dependent upon the time after seeding that the inducer was added. The C3H/10T 1/2 CL8 cells were induced by benz(a)anthracene to a greater extent than the other two cell lines. The high pressure liquid chromatographic profile of benzo(a)pyrene metabolites was qualitatively identical for microsomes from all three cell lines and differed from the metabolism by liver and lung microsomes in that the cells did not produce detectable levels of benzo(a)pyrene-4,5-hydrodiol. The reduced CO cytochrome P-450 difference spectra of control and induced microsomes from all three cell lines showed a characteristic shiftmore » to shorter wavelengths after induction with benz(a)anthracene. The specific activity of cytochrome P-450 in the cell microsomes closely paralled the benzo(a)pyrene metabolizing activity as measured both by the aryl hydrocarbon hydroxylase and high pressure liquid chromatography assays.« less