Variation in inducibility of cytochrome P-450c and aryl hydrocarbon hydroxylase in rat liver, lung, kidney, pancreas and nasopharynx.

The effect of 3-methylcholanthrene (MC) treatment on the cytochrome P-450c content of various rat tissues was examined by measuring the level of immunodetectable P-450c in conjunction with its aryl hydrocarbon hydroxylase (AHH) activity. Immunoblots revealed that P-450d was induced in the nasopharynx and pancreas in addition to its previously reported induction in the liver, lung and kidney. In contrast to P-450c, induction of the immunorelated P-450d was observed only in the liver. The specific content of immunodetected P-450c in the tissue homogenates decreased in the order: liver, nasopharynx, pancreas, lung, kidney. The corresponding AHH activities decreased in the order: liver, kidney, lung, nasopharynx, pancreas. The ratio of AHH activity to P-450c content varied widely among tissues: ratios of 37.2:1.7:0.47:0.04:0.02 were obtained for the kidney, liver, lung, nasopharynx and pancreas, respectively. The absence of a direct relationship between the levels of AHH and P-450c indicates that the extrahepatic activity may partially derive from P-450 forms other than P-450c and/or the specific activity of P-450c varies among different tissues.