The effect of RU 486 on progesterone receptor in villous and extravillous trophoblast.

A total of 60 women with 6-7 weeks' amenorrhoea were randomly allocated to three groups. The women in the first group (control) took a placebo 24 h before undergoing vacuum aspiration. The subjects in the second and third groups were given orally 200 mg of RU 486, 12 or 24 h before surgical interruption of their pregnancy. Villi and decidua were collected and frozen in liquid nitrogen. There were no significant differences in villous cytosolic steroid concentrations between the control and RU 486-treated groups. The RU 486 concentration was lower in villous cytosol than in decidua and serum. The immunostaining of progesterone receptor in villous and extravillous trophoblast was weak and localized in both cytoplasm and nucleus. RU 486 treatment had no effect on the immunostaining of progesterone receptors in trophoblast populations except in the placental bed giant cells, where the weak and diffuse progesterone receptor staining in the cytoplasm of controls seemed to be concentrated in the nucleus after RU 486 treatment. In conclusion, RU 486 might have no effect on the immunostaining of progesterone receptor and on steroid concentrations in villi in vivo.