Immunohistochemical Localization of Cytochrome P4501a in Multiple Types of Contaminant-Associated Hepatic-Lesions in English Sole (pleuronectes Vetulus)

Variations in the expression of cytochrome P450 (CYP) isozymes in cells may affect the response of and consequent toxic effects in those cells during xenobiotic exposure. The expression of cytochrome P4501A (CYP1A), a major inducible CYP in teleosts, was examined immunohistochemically in multiple toxicopathic hepatic lesion types, including neoplasms and several types of preneoplastic foci of cellular alteration (FCA), in English sole (Pleuronectes vetulus) captured from the Duwamish Waterway, a highly contaminated estuary of Puget Sound, WA. Formalin or Bouin's-fixed, paraffin-embedded tissue sections were stained with polyclonal rabbit anticod CYP1A IgG by the avidin-biotin peroxidase complex method; this antibody binds to both Atlantic cod (Gadus morhua) and English sole CYP1A in Western blotting and ELISA, and immunohistochemically-localizes CYP1A in hepatic and other tissues of cod exposed to β-naphthoflavone. CYP1A-associated staining intensity was lower in hepatocellular and cholangiocellular neoplasms, areas of biliary hyperplasia, and normal intrahepatic exocrine pancreas and bile ducts, as compared to histologically normal hepatocellular parenchyma. FCA of basophilic, eosinophilic and clear cell types showed variable staining intensities in comparison to background parenchymal staining, but generally showed reduced CYP1A-associated staining. Staining intensity for a single hemangiopericytic sarcoma showed highly reduced staining for CYP1A. These results, in fish naturally exposed to environmental toxicants, suggest a parallel response between teleosts and mammals with respect to CYP1A expression and resistance to cytotoxicity in cells composing several types of hepatic neoplasms and foci of cellular alteration.