Induced cytochrome P-450 in Fundulus heteroclitus associated with environmental contamination by polychlorinated biphenyls and polynuclear aromatic hydrocarbons

Abstract

Fundulus heteroclitus were collected from two sites in Rhode Island during the non-spawning season and analyzed for hepatic monooxygenase activities and for whole-body concentrations of polychlorinated biphenyls (PCB) and polynuclear aromatic hydrocarbons (PAH). Microsomal protein, total spectral cytochrome P-450 and cytochrome b 5 content did not differ between Seekonk River and Succotash Salt Marsh fish. Ethoxyresorufin O-deethylase (EROD) activity was significantly higher (3-fold) in Fundulus from the Seekonk River than in fish from Succotash Salt Marsh. Similarly, levels of the immunodetectable homolog of P-450E in Fundulus, a representative of the major PAH-inducible P-450 form (P450IA1) in teleosts, were higher in fish from the Seekonk River. In contrast, rates of aldrin epoxidase (AE) activity were the same in fish from the two sites. Concentrations of PCB were 1000-fold, and PAH 60-fold, greater in Seekonk River sediment than in Succotash Salt Marsh sediment. The bioavailability of these contaminants is not known, but the relative degree of contamination in the sediments is reflected in the fish tissues. Fish from both sites had very low concentrations of PAH in their tissues, representing as little as 0·1% of the concentration in the sediment, with tissue concentrations in Seekonk River fish exceeding those of Succotash fish by 4-fold. Polychlorinated biphenyl concentrations in Seekonk fish (1860 ± 176 ng per g dry weight) were 3-fold higher than in Succotash Marsh fish (636 ± 217 ng per g). These concentrations were nearly the same (Seekonk fish) or 300-fold greater (Succotash Marsh fish) than PCB concentrations in the surrounding sediment. The result is consistent with a rapid metabolism of PAH while PCBs appear to be slowly eliminated by these fish. Tissue PCB concentrations in Seekonk River fish were similar to those known to elicit strong P-450 induction in Fundulus. Thus, levels of hepatic P-450E and EROD activity, but not AE activity, reflect relative tissue concentrations of PCB and PAH in Fundulus from two sites. Liver hypertrophy was also observed in Seekonk River fish, indicating that altered liver function may have occurred in these animals.