INDUCTION OF CYTOCHROME P4501A IN THE MUMMICHOG (FUNDULUS-HETEROCLITUS) BY THE POLYCHLORINATED TERPHENYL FORMULATION AROCLOR-5432

Accumulation of the polychlorinated terphenyl formulation Aroclor 5432 in aquatic species has previously been reported. Polychlorinated terphenyls (PCTs) are structurally similar to polychlorinated biphenyls (PCBs), and were used in related applications. However, their biological effects have not been thoroughly studied. Effects of PCT mixtures on levels of hepatic cytochrome P4501A (P4501A) and associated ethoxyresourfin O-deethylase (EROD) activity in the mummichog (Fundulus heteroclitus), a common estuarine fish, were assessed here. Fish were injected intraperitoneally with PCT formulations Aroclor 5432, Aroclor 5460, or the PCB formulation Aroclor 1254, at doses of 0.32 to 100 mg/kg body weight. Elevated levels of P4501A and EROD activity were detected in fish injected with Aroclor 5432 and Aroclor 1254 doses of 32 and 100 mg/kg. Induction resulting from Aroclor 5432 was greater than that caused by equivalent doses of Aroclor 1254. Treatment with Aroclor 5460 did not result in significant induction. Because commercial PCT mixtures contain small amounts of PCBs, the PCB components may have contributed to the induction observed for Aroclor 5432. This work represents the first report of hepatic cytochrome P4501A induction caused by Aroclor 5432 in teleosts and, similar to work in mammalian systems, suggests that the effects of this mixture may be at least partially mediated through Ah receptor binding.