The Effects of Growth Hormone, Thyroxine and Insulin on the Activities of Reduced Nicotinamide Adenine Dinucleotide Phosphate Dehydrogenase, Glucose-6-Phosphatase and Glycogen Phosphorylase in Fetal Rat Liver

Abstract

Growth hormone (GH), thyroxine (T₄) and insulin were injected, in utero into 20.5 day-old rat fetuses to study the effects of these hormones on the activities of liver NADPH dehydrogenase, glucose-6-phosphatase and glycogen phosphorylase. It was found that at 21.5 days of gestation, GH increases the fetal liver glucose-6-phosphatase activity and decreases the liver glycogen Phosphorylase activity. T₄ treatment augments the activity of NADPH dehydrogenase even at 0.3% of the dose shown previously to produce premature elevation of activity. Prior to this experiment T₄ in large doses has been shown to be capable of elevating glucose-6-phosphatase. However, at the lower T₄ dose used, no treatment effect was observed. The fetal rat liver is responsive to insulin at 21.5 days and insulin was able to depress glucose- 6-phosphatase activity, thereby, showing that the influence of insulin on this enzyme begins prior to birth instead of just subsequent to birth.

Key words

Fetal-Enzyme - Growth Hormone - Thyroxine - Insulin