In vivo response of melatonin, gonadal activity and biochemical changes during CYP19 inhibited sex reversal in common carp Cyprinus carpio (L)

CYP19 aromatase is the key enzyme in vertebrate steroidogenesis, catalyzing the conversion of C19 androgens to 17β-estradiol (E2). The objective of the present study was to assess the effect of the CYP19 inhibitors (AIs) fadrozole and anastrozole on gonadal development and sex differentiation in Cyprinus carpio and investigate the possible involvement of in vivo melatonin (MLT) production during sex differentiation. The CYP19 activity in 30 day-post fertilized (30 dpf) fingerlings was inhibited by treating with fadrozole and anastrozole in doses of 100 mg/kg and 200 mg/kg of feed. Gonado-somatic-index (GSI) of fish decreased (P < 0.005) and the changes in GSI was dose dependent. Serum testosterone (T) concentration increased (P < 0.001) after AI treatments and was negatively correlated with serum E2 concentration which decreased (P < 0.005). Morning serum MLT concentration decreased during the period of inhibited CYP19 activity with a positive correlation with E2 concentration. Sex-ratio in anastrazole (200 mg/kg) treated fish were 98.1% males while with fadrozole treatment at the same dose resulted in a 97.1% masculinization. Histological examination of fadrozole-treated fish gonads resulted in detection of atretic follicles and intensified spermiation. The protein and lipid production was depressed in AIs-treated fish. The results suggested that fadrozole and anastrozole both effectively inhibited oogenesis and ovarian development in C. carpio accelerating testicular formation. There was a physiological correlation between CYP19 activity, E2 and MLT synthesis during gonadal development and sex differentiation.