Studies on cytochrome P4501A in early and adult life stages of turbot (Scophthalmus maximus L.)

Cytochrome P4501A (CYP1A) has been investigated extensively in the liver of adults of many different fish species. This study reports the presence and elevation of CYP1A measured as 7-ethoxyresorufin O-deethylase (EROD) activity and protein amount (Western blot — semi-quantified by image analysis) in larval, juvenile and adult turbot (Scophthalmus maximus) after exposure to organic contaminant and model inducers. Basal EROD activity was not detectable in embryos, but increased from 3 day larvae (whole body 13 500g supernatants) through 90 day juveniles (hepatic 13 500g supernatants) to adults (hepatic microsomes), respectively in pmol/min/mg protein (± SEM), 0.57 ± 0.06, 10.8 ± 2.4 and 12.3 ± 4.7. Exposure to 5 ppb benzo[a]pyrene (B[a]P), 1 ppb γ-hexachlorocyclohexane (lindane) and 25 ppb B[a]P caused respectively, 3-, 6- and 2-fold elevation of EROD activity in 4 and 9 day larvae and juvenile stages. Image analysis of Western blots of juvenile samples detected a 3-fold difference in CYP1A protein whereas EROD activity of the same sample varied 4-fold. The results confirm the potential of using CYP1A induction as a biomarker for impact by organic pollution on early developmental stages of fish.