Thyroid Hormone Induction of α-Glycerophosphate Dehydrogenase in Rats of Different Ages

Abstract

The thyroxine-provoked increase in mitochondrial [alpha]-glycerophosphate dehydrogenase ([alpha]-GPD) activity was studied in the liver of rats of different ages. The brain enzyme was also determined. Administration of thyroxine to the mature fetus directly or to the pregnant rat caused a large increase in activity of the fetal liver enzyme. The infant and adult rat livers also exhibited an increase in [alpha]-GPD activity. The brain enzyme of infant and adult rats was unaffected by thyroxine. Actinomycin completely prevented the inducing effect of thyroxine on hepatic [alpha]-GPD, suggesting involvement of RNA in the enzyme Increase. The enzyme in infant liver mitochondria is more sensitive than the adult to the inducing effects of thyroxine.