HEPATIC CELLULAR-DISTRIBUTION OF CYTOCHROME-P-450 IA1 IN RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) - AN IMMUNOHISTOCHEMICAL AND CYTOCHEMICAL STUDY

Monoclonal antibody 1-12-3 reactive against scup (Stenotomus chrysops) cytochrome P450 E (a teleost CYP IA1) has been used to immunohistoche mically localize CYP IA1 within hepatocytes and presumably sinusoidal endothelial and biliary epithelial cells of scup and trout. The goal o f the present study was to extend immunohistochemical studies to the u ltrastructural level determining intracellular locations of CYP IA1 in fish liver. Juvenile trout (5-10 g) were given i.p. injections once ( 50 mug beta-naphthoflavone in cod liver oil; 0.5-ml injectate volume). After 5 days, livers were fixed (0.25% glutaraldehyde) via vascular i n situ perfusion, removed, cut in 100-mum slices, infiltrated, and emb edded in LR White monomer. Ultrathin sections of exposed livers were i ncubated in monoclonal antibody 1-12-3, rabbit anti-mouse IgG, and pro tein G colloidal gold. Membranes of granular, endoplasmic reticulum in perinuclear regions of hepatocytes were consistently labeled. In addi tion, hepatocyte plasma membrane, particularly microvilli at bile cana liculi, was labeled. Biliary epithelial cells were labeled on luminal plasma membrane surrounding biliary passageway. Plasma membrane facing sinusoid and immediately subjacent cytoplasm was labeled in endotheli al cells. Presence of CYP IA1 in sinusoidal endothelium could contribu te to detoxication and/or bioactivation of blood borne chemicals. Gran ular endoplasmic reticulum was not uniformly labeled in hepatocytes. R ather, distribution seemed sequestered within highly specific regions and not dispersed along all membrane surfaces. Localization within bil iary epithelial cells could signify potential of this cell type to bio activate polycyclic aromatic hydrocarbons and may explain the common f inding of biliary as well as hepatocytic tumors of trout liver.