Effects of polychlorinated biphenyls and environmental temperature on in vitro formation of benzo[a]pyrene metabolites by liver of trout (Salmo gairdneri).

Rainbow trout (Salmo gairdneri) held at 7 degrees and 16 degrees were given Aroclor 1254 (PCB) (10 mg/kg body wt) via intraperitoneal injections. The binding of [3H]benzo[a]pyrene (BaP) to deproteinized salmon sperm DNA was assayed (pmoles BaP equivalents per mg DNA per mg protein) using the post-mitochondrial supernatant (S 10) fractions from livers of fish at 24-168 hr after the PCB exposure. Liver enzymes from the untreated fish acclimated at 7 degrees yielded an average binding value (0.37 +/- 0.17) which was significantly greater (P less than 0.05) than the value (0.07 +/- 0.03) for untreated fish at 16 degrees. Liver supernatant fractions from PCB-induced fish acclimated at 16 degrees and sampled at 24-120 hr showed a substantial increase (P less than 0.05) in the binding (average value 2.4 +/- 1.8) compared to the value obtained with untreated fish at 16 degrees. At 24, 48 and 120 hr after the PCB treatment of fish held at 7 degrees, there was no significant increase in the binding value or extent of metabolism of BaP compared to that obtained with the untreated fish at 7 degrees. However, at 168 hr, three of four fish at 7 degrees responded to the PCB treatment with significantly (P less than 0.05) increased binding values (3.3 +/- 1.6). Chromatographic analyses of the ethyl acetate-soluble metabolites revealed that 3-hydroxy BaP and 7,8- and 9,10-dihydrodiols were the major metabolites; K-region metabolites were formed in trace amounts in untreated and PCB-treated fish at both temperatures. No marked qualitative differences were observed in metabolite profiles after the PCB treatment; however, overall metabolism of BaP and production of reactive metabolites by liver enzymes were considerably (P less than 0.05) enhanced in the PCB-induced fish at both 7 degrees and 16 degrees.