Loss of membrane integrity and inhibition of type-I iodothyronine 5'-monodeiodinase activity by fenvalerate in female mouse.

The possible involvement of lipid peroxidation (LPO) in the fenvalerate-induced thyroid dysfunction with special reference to type I 5'-monodeiodinase (5'-D) activity has been worked out. Fenvalerate (40, 80 and 120 mg/kg body weight) enhanced LPO in biomembranes of liver and kidney leading to a decrease in membrane integrity. 5'-D activity and serum concentration of triiodothyronine (T3) were reduced by the highest dose. Serum thyroxine (T4) concentration was decreased in all the three fenvalerate-treated groups, indicating the sensitivity of thyroid gland to this pesticide. A marginal increase in T4 concentration in highest dose-treated group compared to that of the lower one supports the view that the monodeiodination of the phenolic ring of T4 is inhibited by fenvalerate. We suggest the possible inactivation of 5'-D by the generated free radicals in pesticide-treated animals.