Metabolic Actions of Acetic Acid Analogs of Thyroxine and Triiodothyronine.

Abstract

Tetraiodothyroacetic acid (Tetrac) and triiodothyroacetic acid (Triac), injected into thyroidecto-mized rats over several days, have the same order of activity as an equimolar dose of L-thyroxine, as judged from the oxida-tive metabolism of excised tissues,. Triac and Tetrac do not appear to produce an immediate metabolism-stimulating effect, either injected into animals or incubated in vitro with tissue slices. At levels which depress O2 consumption of Ehrlich mouse ascites tumor cells, Triac and Tetrac enhance aerobic and anaerobic glycolyses. However, this effect is not considered specific to the acetate analogs, since thyroxine, triiodothyronine, and a physiologically inactive thyroxine isomer all are capable of producing similar changes.