Immunohistochemical distribution of cytochrome P4501A in larvae and fingerlings of the Siberian sturgeon, Acipenser baeri

In this paper we investigate by means of immunohistochemistry, the tissue d istribution of constitutive cytochrome P4501A (CYP1A), from hatching until 30 days posthatching in developing Siberian sturgeon, Acipenser baeri. For this purpose, a polyclonal (BN-1) antiserum developed against a conservativ e sequence of piscine CYP1A and a monoclonal (C10-7) antiserum directed aga inst cod CYP1A were used on paraffin-embedded samples. From hatching onward s, distinct CYP1A immunoreactivity was distinctly observed in the following tissues and cells: envelope of oil droplets, matrix and syncytium of the y olk-sac, sinusoids, biliary epithelial cells and hepatocytes. In the digest ive tract, buccopharyngeal, oesophageal, gastric and intestinal epithelia, as well as the cytoplasm and brush border of enterocytes were CYP1A-positiv e. Interestingly, gastric glands and melanin-plug present within lumen of t he digestive system were strongly immunoreactive. Kidney (epithelia of rena l tubules), gills (pillar and endothelial cells), skin (epithelial cells), muscle fibres of heart and eye (retina) were positive. In brain, we observe d a strong CYP1A staining in the developing telencephalon and especially in olfactory system, as well as in those nerve fibres running ventrally towar d the posterior brain. A strong CYP1A staining was observed in vascular end othelia of all organs/tissues, especially in the liver. In general, the int ensity of CYP1A immunostaining increased during larval development, suggest ing besides its known metabolic function (endogenous and/or exogenous), a p ossible participation of this heme-protein in control of cell division, reg ulation of growth and differentiation.