The effect of RU 38,486 on progesterone and oestrogen receptor concentrations in the decidua and placenta in early pregnancy.

Decidual and placental concentrations of progesterone and oestrogen receptors in 15 women having medical terminations of pregnancy with a combination of the anti-progesterone steroid RU 38,486 and prostaglandin E1 analogue have been compared with 10 matched controls undergoing surgical aspiration of pregnancy. In the patients treated with RU 38,486, the mean (SD) decidual cytosolic and total progesterone receptor concentrations of 4.3 (5.6) and 7.6 (7.1) fmol/microgram DNA respectively were significantly lower than the levels of 18.5 (14.4) and 22.3 (17.4) fmol/microgram DNA in the control patients. Progesterone receptor concentrations in the placenta were very low in both groups. No significant change in oestrogen receptor concentrations occurred in the decidua or placenta after treatment with RU 38,486. These data indicate that there may be down-regulation of decidual progesterone receptor concentrations following RU 38,486 treatment.