Temporal induction pattern of hepatic cytochrome P450 1A in thermally acclimated dab (Limanda limanda) treated with 3,3',4,4'-tetrachlorobiphenyl (CB77)

Mature male dab (Limanda limanda) acclimated at 10 degrees and 16 degrees C were orally administered a single dose of 0.5 mg/kg 3,3',4,4'-tetrachlorobiphenyl (CB77). At both temperatures, levels of cytochrome P450 1A (CYP1A) protein and 7-ethoxyresorufin O-deethylase (EROD) activity showed a two to six fold induction 40 days after CB77 treatment compared to control groups. Maximum responses of both EROD activity and CYP1A protein for the warm-acclimated fish were observed at 5 days after treatment. For the cold-acclimated fish a slow, progressive elevation for both EROD activity and CYP1A protein was observed and maximum responses were measured 40 days after treatment. Absolute EROD activity and CYP1A protein levels of fish from both temperatures were equally high at 40 days after treatment. Since in the control groups EROD activity and CYP1A protein levels were higher in the cold-acclimated fish, the magnitude of induction was higher in the warm acclimated ones. The highest concentrations of CB77 in muscle of fish from both temperatures were found at 5 and 10 days after treatment. The liver somatic index (LSI) showed 1.5 fold significantly higher values for the fish acclimated at 10 degrees C. Copyright (C) 1996 Elsevier Science Ltd