Immunocytochemical distribution of cytochrome P4501A (CYP1A) in developing gilthead seabream, Sparus aurata.

CYP1A is a major inducible enzyme in the metabolism of xenobiotic substrates. In this paper we investigate by means of immunohistochemistry, the tissue distribution of constitutive cytochrome P4501A (CYP1A) during the period of endogenous nutrition (from hatching until day 4) in developing gilthead seabream, Sparus aurata larvae. For this purpose, a polyclonal antiserum (BN-1, Biosense Laboratories) directed against conserved piscine CYP1A sequences was used on paraffin-embedded sections from seabream larvae. From hatching onward, CYP1A immunoreactivity was observed in the following tissues and cells: syncytial, oil-globule envelopes and matrix of the yolk-sac, kidney (epithelia of renal tubules), cardiac muscle cells, skin epidermal cells, troncal musculature, enterocytes of different intestinal regions, goblet cells of the bucco-pharyngeal region, gill epithelial cells and the endothelia of the vascular system of various tissues (especially from liver and brain). Moreover, eye (retina), olfactory epithelium and some positive nerve fibers located in the proximity of the olfactory bulbs and running ventrally toward the posterior brain were strongly CYP1A immunoreactive. In general, the intensity of immunostaining increased with larval development.