SUMMARY
Glycogen synthetase, phosphorylase and glycogen were determined biochemically in the smooth muscle of the rat uterus following a single s.c. injection (10 μg.) of oestradiol dipropionate. The ovariectomized animals were killed 6, 12, 24, 48, 72 and 96 hr. after the hormone treatment. From 12 to 96 hr. glycogen synthetase activity was significantly greater than in the untreated control rats. Phosphorylase activity was significantly less than in the controls at 12 hr. and greater from 48 to 96 hr. After the initial drop, control phosphorylase values were obtained between 24 and 48 hr. From 12 to 96 hr. the glycogen concentration was greater than in the control animals.
The results show that oestrogen increased glycogen synthetase activity in the smooth muscle of the uterus soon after the hormone treatment, and with the increase in enzymic activity the glycogen concentration was also increased. They indicate that, during the early phase of glycogen synthesis, oestrogen stimulates glycogenesis by increasing glycogen synthetase activity and suppresses glycogenolysis by inhibiting phosphorylase activity. The glycogen concentration at later stages did not alter significantly, and this may have been due to the build-up and breakdown of the carbohydrate by the action of glycogen synthetase and phosphorylase, respectively.
Phosphorylase activity in rat uterus after catecholamine administration
