HEPATIC P4501A ACTIVITY, PLASMA SEX STEROIDS, AND GONADAL STEROIDOGENESIS IN VITRO IN YELLOW PERCH EXPOSED TO 3,3?,4,4?,5-PENTACHLOROBIPHENYL
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Yellow perch were given a single intraperitoneal injection of polychlorinated biphenyl (PCB) 126 dissolved in corn oil at nominal concentrations of 0, 10, 100, and 500 mug/kg body weight. Following the injection, the fish were held for four weeks under photothermal conditions characteristic for Ohio, USA, and fed a commercial fish food. Thereafter, they were sacrificed to examine the PCB 126 concentrations in the liver and to assess the contaminant effects on hepatic P4501A activity, reproductive hormones in plasma, and steroidogenic potential of gonads. The administered doses resulted in liver concentrations of 0.8 (corn oil control), 12.1, 38.9, and 174.5 mug/kg wet tissue weight. Hepatic P4501A indices were differentially affected depending on both the PCB 126 dose and fish gender. In untreated fish, the P4501A protein and ethoxyresorufin-O-deerhylase activity were several times lower in females than in males. In treated males, the hepatic P4501A was inhibited by all three PCB 126 doses. In females, a significant P4501A induction occurred in those dosed with 10 mug/kg, while no changes were found in the two higher-dosed female groups in comparison to controls. A significant negative correlation was observed between hepatic P4501A indices and gonad somatic indexes values and plasma estradiol concentrations. The PCB 126 administration produced alterations in concentrations of plasma sex hormones in females but not in males. The in vitro steroidogenic potential of the female and male gonads was not affected by the in vivo PCB 126 treatment.