Brain cytochrome P450 aromatase activity in roach (Rutilus rutilus): seasonal variations and impact of environmental contaminants.

P450 aromatase catalyses the conversion of C19 androgens to C18 estrogens which is thought to be essential for the regulation of the reproductive function. In this study, brain aromatase activity (AA) was measured monthly over a reproductive cycle in wild roach (Rutilus rutilus) sampled in a reference site in Normandy. AA peaked during the breeding season, reaching 35 fmol mg(-1)min(-1) in both male and female fish, and was low during the rest of the year except for a significant rise in October. AA was correlated with ovary maturation (measured either as gonado-somatic index or by histological analysis of the gonads) and plasma sex-steroid levels (11-ketotestosterone in males and 17-β-estradiol in females). Measurements of AA in polluted sites showed that activity was significantly upregulated in sites with fish showing high levels of plasma vitellogenin and large proportion of intersexuality (20-50%) thus suggesting the occurrence of estrogenic compounds and their involvement in AA modulation. Copyright Â