Immunohistochemical localization of cytochrome P4501A in developing turbot, Scophthalmus maximus

In order to interpret toxic responses of fish embryos and larvae to xenobiotics, knowledge on biotransformation capacities of fish early life stages is important. This study examines by means of immunohistochemistry the expression of cytochrome P4501A (CYP1A), a major inducible enzyme of xenobiotic metabolism, in the organs of turbot, Scophthalmus maximus, larvae. A polyclonal antiserum (BN-1, Biosense Laboratories), prepared to conserved piscine CYP1A sequences, was used to stain the enzyme in paraffin-embedded tissue sections. Strong immunoreactivity for CYP1A was obtained in liver parenchymal cells, but hepatic sinusoideal epithelia also responded positively. Extrahepatically, CYP1A immunoreactivity was found in the kidney tubulus epithelium, in cardiac muscle cells, in the retina, as well as in endothelia of gill filaments, glomerulum, heart, brain and muscles. The results indicate that the tissue distribution patterns of CYP1A in larval turbot are comparable to those found in the adults.