Immunohistochemical localization of cytochrome P-450IA1 induced by 3,3',4,4'-tetrachlorobiphenyl and by 2,3,7,8-tetrachlorodibenzoafuran in liver and extrahepatic tissues of the teleost Stenotomus chrysops (scup).

The regulation of different cytochrome P-450 forms and their functions in different organs and cell types could determine the susceptibility of those cells and organs to toxic effects of xenobiotics, including chemical carcinogenesis. Here we describe the cellular localization of cytochrome P-450E (P-450IA1) induced in 10 major organs or organ systems of a marine vertebrate species, the fish, Stenotomus chrysops (scup). Scup were injected ip with 3,3',4,4'-tetrachlorobiphenyl (TCB) at 1 mg/kg, or with 2,3,7,8-tetrachlorodibenzofuran (TCDF) at 3 micrograms/kg. Induction was verified by Western blot analysis of microsomes from selected organs (liver, kidney, and gill) using monoclonal antibody (MAb) 1-12-3 to scup P-450IA1. The localization of P-450IA1 was subsequently determined in sections prepared by standard histological methods (10% buffered formalin fixation, paraffin embedding), and stained with MAb 1-12-3 and peroxidase-labeled second antibody. P-450IA1 was induced in epithelial and endothelial cells in liver (including pancreatic tissue), kidney, gill, gut, spleen, testis, and ovary. Induction also was detected in endothelial cells, but not other types, in heart, brain, and red muscle. In heart, the staining was present in the endocardium as well as in the endothelium of the coronary vasculature and great vessels. Although TCDF and TCB both induced P-450IA1 in various cells of all organs examined, the effect of TCB was in most cases greater than that of TCDF. This may be due to a relatively higher TCB dosage. A wider staining distribution was seen in gut, gill, kidney, and gonad of TCB-treated fish, which might be explained by a greater penetration, or by excretion of parent TCB, as opposed to TCDF. In any case, the results show that these important environmental agents induce P-450IA1 in generally similar patterns in all organs examined. The common finding of a strong induction of P-450IA1 in endothelial cells in all organs examined supports the suggestion that the endothelium may be a primary site of P-450IA1 induction.