Effect of polychlorinated biphenyls (PCB) on metabolism of thyroid hormone in Wistar rats.

Recently, goitrogenic action of DDT and P, P,-DDT on avian thyroid have been reported by Jefferies and French1,2). Fregly et al.3) observed an increase in thyroid weight of male rats by chronic treatment with DDT. Since these reports are based on the histological evidence and the measurment of thyroid weight, the mechanism of the action of DDT and its analogues is not known at present. DDT and polychlorinated biphenyls are the important chlorinated hydrocabons in the environmental contaminant and were observed to induce the drug metabolizing enzyme in hepatic microsome.4) This evidence prompted us to study the goitrogenic action of PCB (using Kanechlor KC-400). KC-400 mainly consists of tetrachlorobiphenyls and is the contaminant in the rice-oil which caused Yusho (PCB poisoning) in Japan.5)