Estradiol benzoate (EB-5 mg/kg) or
testosterone propionate (TP-50 mg/kg) administration to sexually immature rainbow trout resulted in an increase in liver weight to
body weight ratios, and a diminution in hepatic microsomal
benzphetamine-N-demethylation (BeND), ethoxycoumarin- and
ethoxyresorufin-O-deethylations (ECOD,
EROD) and
cytochrome(s) P-450 content when compared to
corn oil-pretreated controls. A low dose of TP (2 mg/kg) caused an increase in
cytochrome(s) P-450 content but had no effect on the selected
monooxygenase activities. EB administration prior to treatment with 150 mg/kg
beta-naphthoflavone caused a dose-dependent decrease in the magnitude of induction of
cytochrome(s) P-450 and associated catalytic activities. These data suggest that the sex differences in monooxygenation observed in prespawning trout are mediated via the sex
steroids and that fish may respond differently to inducers depending on their reproductive state at the time of exposure. Administration of the synthetic
steroid, pregnenolone-16 alpha-carbonitrile (
PCN), resulted in an increase in BeND and ECOD but had no effect on
EROD or
cytochrome(s) P-450 content.