Comparison of Activity of Thyroxine and 3,5,3'-Triiodothyronine

Abstract

A comparison of 3,5,3[image]-triiodo-L-thyronine with thyroxine has shown that triiodothyronine has comparable activity on a molar basis in inhibiting the cupric ion catalyzed oxidation of ascorbic acid and in stimulating the oxidation of succinate by rat heart homogenates. On a wt. basis it produced a slight decrease in survival time of mice in an anoxic test when compared to thyroxine. Both compounds increased the metabolism of a normal rat to the same degree. The Folin-Ciocalteu test for the phenolic hydroxyl group demonstrates that this group in triiodothyronine is more reactive than the similar group in thyroxine.