Induction of Mitochondrial -Glycerophosphate Dehydrogenase by Thyroid Stimulating Hormone and Thyroid Hormone Analogues.

Abstract

The level of mitochondrial L-alpha-glycerophosphate dehydrogenase of rat liver is greatly decreased after hypophysectomy. The lowered enzyme level in these animals was rapidly restored after administration of a single dose of L-triiodothyronine. Thyroid-stimulating hormone given to hypophysectomized rats, gradually increased the enzyme activity and this response depended on both the dosage and the duration of treatment. A number of iodine-containing compounds were used to evaluate the chemical specificity of structure of inducing molecules. The results showed a good correlation between the inducing ability of these analogues and its hormonal activity. The reported observations support the idea that mitochondrial L-alpha-glycerophosphate dehydrogenase activity is controlled by the thyroid hormone. The “admixture test” failed to show the presence of an activator or the absence of an inhibitor in the mitochondrial preparation obtained from L-triiodothyronine-treated animals. The present observations further support the previous suggestion that the increase of mitochondrial L-alpha-glycerophosphate dehydrogenase activity after the administration of thyroid hormone may result from acceleration of enzyme synthesis even when stimulated by physiological amounts of the hormone.