Lead inhibits type-I iodothyronine 5'-monodeiodinase in the Indian rock pigeon Columba livia: A possible involvement of essential thiol groups

A study has been made to reveal the mode of action of lead inhibiting type-I iodothyronine 5'-monodeiodioase (5'-D) activity in the Indian rock pigeon, Columba livia. Administration of lead acetate (6 mg/kg body weight/day) for 20 days decreased 5'-D activity and glutathione content in the Liver and kidney homogenates. It also reduced the serum concentration of 3,3', 5-triiodothyronine (T-3) with a marginal increase in serum thyroxine (T-4). Hepatic and renal lipid peroxidative process increased significantly following lead treatment, whereas the levels of antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT) were decreased. The possible involvement of lipid peroxidative process in the inhibition of 5'-D activity in Columba livia is suggested.