Development of assessment method for complex aquatic pollution using xenobiotic metabolic enzyme in liver of aquatic mammals

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The correlation between the residual chlorinated hydrocarbon levels and the cytochrome P450 expression levels in livers and the thyroid function were studied in largha seals and ribbon seals from the coast of Hokkaido. The largha seals showed the significant levels of residual non-ortho mono-ortho coplanar PCB homologues in their epidermis with the hepatic enzymatic activity of ethoxyresorfin deethylation (EROD). The Western blot analysis indicated that the coplanar PCB homologue levels were related with those of P4501A-like protein. The ribbon seals, on the other hand, did not give such correlations. These results suggested that coplanar PCB induces P4501A-like enzyme in the largha seals, which is basedon the specific mechanism in this species.The quantities of total thyroxine, free thyroxine, total tri-iodo thyronine and free tri-iodo thyronine were measured in both seal blood withthose ages. The T3 was were found to correlated negatively with most chlorinated organic compounds. Especially, the PCB170 and PCB18O gave the significant and negative correlation with total T3 . Though the thyroid hormone is generally known to decrease by the aging, the values observed here exceeded them. It was anticipated that there is the serious effect for growth and reproduction of seals.