Effects of Thyroidectomy and Triiodothyronine Administratio on Oxidative Enzymes in Rat Liver Microsomes

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Abstract
1. Effects of thyroidectomy and injection of a physiological dose of triiodothyronine to the thyroidectomized animal on the levels of various oxidative enzymes in rat liver were studied. 2. All the microsomal activities concerned with NADPH oxidation were markedly decreased after thyroidectomy and elevated rapidly following the hormone administration. 3. Microsomal hemoproteins, cytochrome b5 and P-450, and microsomal NADH oxidizing activities remained unchanged for 10 to 15 days after thyroidectomy, but increased abruptly thereafter. The elevated levels could be reduced by the hormone injection. 4. Alcohol dehydrogenase [EG 1.1.1.1] of the soluble fraction showed similar, though not identical, responses to the microsomal hemoproteins. 5. The contents of cytochromes c+c1 and, to a lesser extent, of cytochrome a showed a tendency of gradual decrease after thyroidectomy, and returned to the normal levels on the hormone injection. 6. Soluble NADH diaphorase and mitochondrial cytochrome b were not affected by thyroidectomy and triiodothyronine administration.