Interaction of benzo(a)pyrene and cadmium on GSH-S-transferase and benzo(a)pyrene hydroxylase in the black sea bassCentropristis striata

The effect of benzo(a)pyrene (BaP) and cadmium (Cd) upon the hepatic enzymes, BaP hydroxylase and GSH-S-transferase, was investigated in black sea bass. Intraperitoneal (ip) injections of BaP produced a significant increase in BaP hydroxylase activity in the microsomal fraction and GSH-S-transferase activity in the cytosol. Administration of Cd alone had no effect on either enzyme. However, when both Cd and BaP were injected (ip) in the fish, Cd had an inhibitory effect on the activity of these hepatic enzymes. Pretreatment of fish with a low dose of Cd (0.42 mg/kg) prior to injection of BaP and Cd produced a 30% increase in GSH-S-transferase activity and a 50% reduction in BaP hydroxylase activity when compared to fish injected with BaP alone following Cd pretreatment. Thus, a low dose of Cd was effective in producing a tolerance to a subsequent Cd challenge for the enzyme GSH-S-transferase but not for BaP hydroxylase. In contrast, fish pretreated with a high dose of Cd (2.5 mg/kg) prior to BaP treatment alone or with Cd displayed no difference in either enzyme activity. The implications from this study on the exposure of black sea bass to two xenobiotics, Cd and BaP, indicate that BaP hydroxylase may not serve as a good monitor for hydrocarbon pollution in the presence of Cd.