Estrogen Control of Carbohydrate Metabolism in the Rat Uterus: Pathways of Glucose Metabolism

Abstract

The utilization of glucose-l-14C and glucose-6-14C by uterine segments removed from ovariectomized rats at various times after treatment with 5.0 [mu]g of 17 [beta]-estradiol has been evaluated. Activities of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (EC 1.1.1.44) were also determined in these tissues. While total activity of both enzymes (U/uterus) remained constant for 6 hr. after estrogen administration, a 2-fold increase occurred by the 12th hr. Specific activity (U/mg protein) of both enzymes decreased during the first 6 hr. Thus, induction of these enzymes is not among the very early uterine responses to 17 [beta]-estradiol. Formation of CO2 in vitro from carbon atoms 1 and 6 of glucose by uterine segments 2 hr. after estradiol treatment is greater than that by control and 6-hr. post-estrogen-treated segments. Between 6 and 24 hr. the increased CO2 production from glucose is primarily from carbon atom 1. The ratio of carbon 1 to carbon 6 incorporated into CO2 increases linearly with time after estrogen administration. These data suggest 2 estrogen-sensitive mechanisms for control of glucose metabolism. Incorporation of carbon atoms 1 and 6 of glucose into lipid is equal and increases linearly with time. Incorporation of carbon atoms 1 and 6 of glucose into protein occurs at similar rates for 6 hr. after estrogen administion. Thereafter a significant increase in incorporation of carbon 1 over carbon 6 is observed. The incorporation of carbon atom 1 of glucose into RNA parallels its incorporation into CO2. The same is true of carbon atom 6.