An investigation of the endometrial enzymes glycogen synthetase and glycogen phosphorylase in relation to the menstrual cycle, contraception and early pregnancy

Buckingham, M.S (1980) An investigation of the endometrial enzymes glycogen synthetase and glycogen phosphorylase in relation to the menstrual cycle, contraception and early pregnancy. University of Southampton, Doctoral Thesis.

Abstract

The activities of the endometrial enzymes glycogen synthetase and glycogen phosphorylase were determined by the measurement of the incorporation of radioactive glucose into glycogen. The optimum experimental conditions for the methods were investigated and the sensitivities of the assays established.Normal women were studied at various stages of the menstrual cycle and the effects of contraception in the form of copper bearing or inert intrauterine devices and the combined pill investigated. Plasma oestradiol and progesterone levels were correlated with the enzymes' activities by studying a group of women in the mid-luteai phase of the cycle. Finally the activities of the enzymes in early pregnancy were investigated. The menstrual cycle did not affect the activities of either enzyme significantly in the normal group of women. In women using contraception, the menstrual cycle again had no significant effect on the enzymes' activities, but there was an overall decrease in the activity of glycogen synthetase and an increase in that of glycogen phosphorylase. There was a significant difference between copper bearing and inert intrauterine devices in terms of glycogen synthetase activity but glycogen phosphorylase activity was not affected. The use of oral contraception had the same effect as intrauterine devices on glycogen synthetase activity but induced a significantly greater decrease in glycogen phosphorylase activity. A positive correlation was found between plasma progesterone levels and glycogen synthetase activity. No correlation was found between plasma oestradiol levels and glycogen synthetase activity and neither plasma hormone had a significant correlation with the activity of glycogen phosphorylase. No change was found in glycogen synthetase activity in early pregnancy but that of glycogen phosphorylase increased significantly. The activities of these endometrial enzymes in normal women have therefore been established and the influence of plasma progesterone and oestradiol levels determined. Intrauterine devices and oral contraception induce changes in the activities of both enzymes although the relationship between these findings and their contraceptive effect is uncertain.

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