Effects of Estradiol on Glycogen Synthetase in the Rat Uterus

Oophorectomized rats were sacrificed 6 and 16 hr after a single subcutaneous injection of 2.5 μg of estradiol. Uterine glycogen content and UDPG-glycogen synthetase activity were determined in both groups of animals. Uterine water and glycogen content were increased at both 6 and 16 hr after administration of estradiol. At 6 hr the glucose-6-phosphate independent form of UDPG-glycogen synthetase was also increased, whereas total enzyme activity was unchanged. At 16 hr uterine enzyme activity in the treated rats did not differ significantly from that in the control animals. Estradiol had no effect on liver glycogen synthetase. Progesterone administered 6 hr prior to sacrifice did not affect uterine glycogen synthetase. These data demonstrate an in vivo effect of estradiol on the ratelimiting step in glycogenesis and suggest a mechanism for the estradiol-induced increase in uterine glycogen content. (Endocrinology78: 786, 1966)