LOW HEPATIC 7-ETHOXYRESORUFIN-O-DEETHYLASE (EROD) ACTIVITY AND MINOR ALTERATIONS IN RETINOID AND THYROID-HORMONE LEVELS IN FLOUNDER (PLATICHTHYS-FLESUS) EXPOSED TO THE POLYCHLORINATED BIPHENYL (PCB) MIXTURE, CLOPHEN A50

The effect of the polychlorinated biphenyl (PCB) mixture Clophen A50 o n hepatic cytochrome P4501A1 dependent EROD (7-ethoxyresorufin-O-deeth ylase) activity, plasma thyroid hormone levels and plasma, kidney and liver retinoid concentrations of the euryhaline flatfish flounder (Pla tichthys flesus) was determined 2 and 10 days after i.p. (intraperiton eal) injection with 20, 100 and 500 mg Clophen A50/kg body weight. No effect of Clophen A50 on total cytochrome P450 content in founder live r was observed at both time points. A six-fold, dose-dependent, signif icant increase in EROD activity was found at exposure day 10 in flound er receiving 100 or 500 mg Clophen A50/kg body weight. Plasma retinol concentrations were not altered at both time points after Clophen A50 administration, whereas renal retinol levels showed a minor dose-relat ed increase at day 2 and day 10 of exposure. Significant alterations i n hepatic retinoid concentrations were observed, which were not depend ent on the nose of PCB administered In addition Clophen A50 administra tion did not result in a dose-related alteration of total T-4 concentr ations in plasma. Total T-3 concentrations in plasma were only signifi cantly increased at day 2 after exposure, whereas free T-4 concentrati ons were increased at both time points after Clophen A50 administratio n. These data indicate that with regard to the parameters investigated and in contrast to other fish species studied, the founder is not a s ensitive species to PCB exposure. Copyright (C) 1996 Elsevier Science Ltd