INHIBITION OF OESTROGEN-INDUCED INCREASE IN HEPATIC AND UTERINE GLYCOGEN BY PROGESTERONE IN THE RAT

Abstract

ABSTRACT The effects of progesterone in two different doses (2 mg and 4 mg/rat/day) given alone and in combination with 17β-oestradiol (0.5 μg/rat/day) for 21 days, on ovariectomized rat liver and uterine glycogen were investigated. The food intake and blood glucose level were also studied under these experimental conditions. The liver and uterine glycogen and weight increased during the oestrous stage of the normal rat and following oestrogen treatment of the ovariectomized rat. Progesterone when given in combination with oestrogen inhibited the oestrogen-induced increase in glycogen of these organs and also the weight of the uterus proportionally to the doses. Moreover, progesterone by itself reduced both the concentration and total uterine glycogen of the ovariectomized rat. The food intake and blood glucose level of ovariectomized animals increased after the administration of progesterone alone or in combination with oestrogen. Nevertheless, progesterone alone was more effective in increasing the food intake than in combination with oestrogen, while it was less effective in raising the blood glucose level. It can be concluded from this study that progesterone inhibits the glycogenic effects of oestrogen in the liver and uterus of the ovariectomized rat. Moreover, progesterone by itself inhibits uterine glycogen accumulation in these animals. This glycogenolytic effect of progesterone occurs in the presence of hyperphagia and hyperglycaemia. A possible involvement of the adrenal medulla in these conditions is discussed.