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

研究了北海道沿岸大斑海豹和带状斑海豹肝脏中残留氯代烃水平与细胞色素P450表达水平及甲状腺功能的相关性。大叶海豹表皮中存在大量非邻位单邻位共面PCB同源物，其肝脏酶活性为乙氧基间苯甲醚去乙基化（EROD）。Western blot分析显示共面PCB同源物水平与p4501a样蛋白相关。另一方面，带状封条没有给出这样的相关性。这些结果表明，共面多氯联苯在大叶藻中诱导p4501a样酶，其作用机制是基于大叶藻的特异性机制。测定了不同年龄海豹血中总甲状腺素、游离甲状腺素、总三碘甲状腺原氨酸和游离三碘甲状腺原氨酸的含量。T3与大部分含氯有机化合物呈负相关。其中PCB170、PCB18O与总T3呈显著负相关。虽然一般认为甲状腺激素会随着年龄的增长而下降，但这里观察到的数值超过了它们。预计会对海豹的生长和繁殖造成严重影响。

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.