Interaction of ethanol and thyroxine on mitochondria

Abstract

Thyroxine can stimulate mitochondrial swelling and uncouple oxidative phosphorylation. It was observed that ethanol inhibits both spontaneous and thyroxineinduced mitochrondrial swelling. The antiswelling activity of ethanol is manifested during mitochondrial respiration both in the presence and absence of phosphorylation. Ethanol was observed only to block thyroxine-induced swelling; it could not reverse the swelling. Ethanol also blocked Ca ++ and phosphate-induced swelling. Therefore, the antiswelling activity of ethanol is more generalized than that of serum albumin. It is concluded that the ethanol antagonism of mitochrondrial swelling produced by various agents is probably dependent on the fact that ethanol alone inhibits swelling; ethanol is therefore a pharmacological antagonist of agents that induce swelling. In addition to inhibiting swelling, ethanol also blocks uncoupling of oxidative phosphorylation by thyroxine and Ca ++ but not by salicylate. These observations were interpreted to indicate that ethanol affects oxidative phosphorylation only indirectly by blocking mitochondrial swelling. The observed effects of ethanol on mitochrondria are discussed in terms of reports on the ability of thyroid hormone to antagonize acute alcohol intoxication in man, and the ability of ethanol to block effects of Ca ++ on smooth muscle.