[Effect of RU 486 on glycogen metabolism in endometrium]

To elucidate the effect of the antiprogesterone steroid RU 486 (RU) on endometrial glycogen metabolism, a dose of 30 mg/kg of the agent was administered to pregnant rats on Day 2 (group 1) or Day 4 (group 2) of pregnancy, and glycogen content, glycogen synthetase (GS) and glycogen phosphorylase (GP) activities in the endometrium were investigated on Day 6. In addition, serum ovarian steroid hormones and the number of implantation sites were evaluated. The glycogen content in the endometrium in group 1 and group 2 decreased significantly (p less than 0.02 and p less than 0.05) compared with the control group. The total GS activity in the endometrium in group 1 decreased significantly (p less than 0.05). On the other hand, the independent GS activity in group 2 increased significantly (p less than 0.05) compared with the control group. The active GP activity in group 1 increased markedly, and the total GP activity increased significantly (p less than 0.05) compared with the control value. In group 2, the active and total GP activities increased significantly (p less than 0.01 and p less than 0.02) compared with the control values. Serum progesterone (P) concentrations in group 1 and group 2 were significantly (p less than 0.05 and p less than 0.05) lower than those in the control groups 2 days after the RU administration, and implantations were significantly (p less than 0.01 and p less than 0.01) inhibited. These results suggest that RU 486 affects endometrial glycogen metabolism, resulting in the prevention of implantation.