The concurrent induction of hepatic alpha-glycerophosphate dehydrogenase and malate dehydrogenase by thyroid hormone.

Abstract

Abstract 1. 1. The 8–10-fold increase in hepatic L -α-glycerophosphate dehydrogenase ( L -glycerol-3-phostphate: cytochrome c oxidoreductase, EC 1.1.2.1) and soluble malate dehydrogenase ( L -malate: TPNH oxidoreductase, EC 1.1.1.40) which occurs as a result of thyroid hormone administration, is inhibited by ethionine, actinomycin D and cycloheximide. This suggests that thyroid hormone induces the synthesis de novo of these enzymes. 2. 2. The half-life of the malate dehydrogenase and L -α-glycerophosphate dehydrogenase in the hyperthyroid state has been estimated to be 4 days. 3. 3. 5-Fluorouracil had no effect on the calorigenic response or the thyroid hormone-induced increase in malate dehydrogenase or L -α-glycerophosphate dehydrogenase in normal or partially hepatectomized rats. 4. 4. The induction of malate dehydrogenase by thyroid hormone was highly dependent upon the type and amount of dietary carbohydrate, whereas the induction of L -α-glycerophosphate dehydrogenase was affected by the protein content of the diet. 5. 5. Starvation decreased the normal levels of both malate dehydrogenase and L -α-glycerophosphate dehydrogenase, but did not affect the L -α-glycerophosphate dehydrogenase response to thyroid hormone; fastomg partially prevented the induction of malate dehydrogenase by thyroid hormone.