Enhanced in vitro hepatic glucuronidation of thyroxine in rats following cutaneous application or ingestion of polychlorinated biphenyls

Abstract

In rats four daily skin applications of a 30% solution of a polychlorinated biphenyl (PCB) mixture in mineral oil or of a microscope immersion oil, containing 34% PCB, led to increases in liver weight, protein concentration of the 10 000 × g supernatant fluid of liver homogenates and the in vitro glucuronidation of thyroxine (T₄) by the supernatant fluid, whether related to liver weight or to protein concentration in the reaction mixture. Similar effects occurred after feeding 250 ppm (mg/kg) of PCB in either Purina chow or a low-iodine diet for 11 days. It is concluded that increased hepatic T₄ glucuronidation contributes to the enhanced biliary excretion of T₄ previously observed in PCB-treated rats.