TISSUE AND SERUM LEVELS OF STEROID-HORMONES AND RU-486 AFTER ADMINISTRATION OF MIFEPRISTONE

The present study was designed to examine the effect RU 486 administra tion on steroid hormone levels in serum and decidua. Sixty women at 6- 7 weeks gestation were divided into three groups. The first group took a placebo 24 hours before interruption of pregnancy. The other two gr oups took 200 mg mifepristone 12 and 24 hours before the surgical proc edure, respectively. The concentrations of steroids and mifepristone w ere measured by radioimmunoassay or high performance liquid chromatogr aphy. Mifepristone treatment increased the levels of estradiol, cortis ol and testosterone in serum and decidual cytosol (p<0.05 or p<0.01). A minor elevation in progesterone level was observed but was not stati stically significant. The tissue levels of progesterone, estradiol and testosterone were much higher than the serum levels, whereas RU 486 c oncentration in the tissue was only one-third of the serum level. In a ddition, the RU 486 level in decidual cytosol was of the same order as that of progesterone. This competitive concentration was not achieved in chorionic villi in our previous observation, explaining why mifepr istone exerts its predominant effect on decidua rather than villi. It is concluded that RU 486 reached an effective inhibitory concentration in decidua and had significant effects on the endocrine milieu.