3,5 Diiodothyroacetic Acid Mobilization of Rat Liver Lipid and Relative Toxicity of Oral Triac and Triprop

Summary

Maximal mobilization of previously elevated liver cholesterol and total lipid depots was achieved by feeding 5 mg% 3,5 diodothyroacetic acid (diac) in a 30% casein diet. An increase from 19% to 30% casein enhanced the lipid mobilization rate, but reduction of the fat content from 26% to 5% lard had little effect when diac was given. Plasma cholesterol concentrations were reduced slightly by diac feeding, but did not reach those levels seen in chow controls. Triac and triprop were found to be more calori-genically active and more toxic than thyrox-ine when fed in a high fat-cholesterol diet whereas they are known to be only 20% and 10% as active as thyroxine when injected subcutaneously into rats on a chow diet. Both route of administration and composition of the diet with respect to the existence of naturally occurring antithyrotoxic factors may be important in determining the relative calori-genic and cholesterol reducing activities of various thyroxine analogues.