Polychlorinated biphenyls concentration and cytochrome P-450E expression in winter flounder from contaminated environments

Abstract

Reproductively mature winter flounder ( Pseudopleuronectes americanus) were collected from three Northeastern US sites with different degrees of polychlorinated biphenyl (PCB) and polynuclear aromatic hydrocarbon (PAH) contamination. Liver PCB concentrations (measured by capillary electron-capture gas chromatography) in fish collected in 1987 and 1988 at New Bedford Harbor (NBH) ranged from 7·4 to 191 μg/g dry wt; at Gaspee Point 3·9–17·7 μg/g; and at Fox Island 1·6–15·1 μg/g. Levels of ethoxyresorufin O-deethylase (EROD) activity were similar in fish of the same reproductive status from the three sites; however, immunoquantitated P-450E homolog (the EROD catalyst) content was significantly higher in NBH fish. This suggests that P-450E catalytic activity is being suppressed in the livers of the NBH animals. Recent studies in our laboratory indicate that competitive inhibition of P-450E catalytic activity by specific PCB congeners is one likely mechanism of this suppression. Hepatic EROD activity and P-450E content were significantly lower in gravid females (EROD, 0·10–0·69 units per nmol P-450; P-450E, 8·4–19% of spectral P-450) than in spent females (EROD, 1·94–3·49; P-450E, 48–109%), and ripe males (EROD, 1·86–3·41; P-450E, 48–84%) at all sites. This is consistent with a hormonal effect on P-450E expression, and thus EROD activity, in gravid females. The data indicate a complex relationship between levels of EROD activity, or P-450E, and tissue PCB concentrations in highly contaminated fish. How these variables are linked to altered endocrine or gonadal function is not yet known.