Cervical smooth muscle contractile activity after treatment with mifepristone and progesterone

Effects of mifepristone and progesterone on collagen synthesis in the human uterine cervix

Antiprogestins are used to induce first trimester abortion and to dilate the cervix before vacuum aspiration. Cervical dilatation is associated with profound changes in the connective tissue. In what respect antiprogestins interfere with this process has hitherto been sparsely investigated. The aim of present study was to examine the influence of the antiprogestin mifepristone on cervical collagen synthesis in nonpregnant, early and late pregnant women. The effects were compared with those of progesterone. The content of collagen in cervical tissue was determined by measuring hydroxyproline. Collagen synthesis was studied in vitro either by incubation of cervical tissue specimens from women, pretreated with mifepristone in vivo, in the presence of 14C-proline or by incubation of cervical tissue of not pretreated women in the presence of the isotope and mifepristone or progesterone. Pretreatment with mifepristone, but not progesterone, induced a significant increase in cervical dilatation. The cervical concentration of collagen was not altered after mifepristone administration. Pretreatment with mifepristone did not quantitatively influence the time course of radiolabeling in vitro or the pattern of radiolabeling in different protein components as revealed by electrophoresis. In vitro mifepristone, like progesterone, reduced the incorporation of 14C-proline. From the present data we conclude that mifepristone pretreatment in connection with first trimester abortion is not associated with any major changes, qualitatively or quantitatively, of collagen synthesis. However, we cannot exclude that mifepristone still may affect the de novo formation of collagen since mifepristone, administered in vitro, did reduce collagen synthesis.

Cervical mucus concentration of prostaglandins E2 and F2 alpha after pretreatment with mifepristone in the first trimester of pregnancy

Cervical dilatation and softening after pretreatment with mifepristone are well documented. As this effect is similar to that observed after local application of prostaglandin E2 (PGE2) it is tempting to speculate that the effect of mifepristone is mediated via an increase of the endogenous secretion of prostaglandins from the cervical mucosa. Eighteen healthy women in the first trimester of pregnancy were treated with oral mifepristone (200 mg) 48 and 24 hours before legal abortion by vacuum aspiration and 18 women in the same age of gestation without any pretreatment served as controls. Cervical mucus was collected for measurement of prostaglandins by radioimmunoassay before administration of the drug and in connection with vacuum aspiration. The cervical dilatation at the time of surgery was significantly increased in women given mifepristone as compared with untreated women (7.6 versus 5.8 mm). The wet weight of collected cervical mucus was significantly increased in mifepristone treated women. The amount of PGE2 and prostaglandin F2 alpha per sample was unchanged in mifepristone-treated women, whereas the concentration was lower as an effect of dilution due to an increased yield in cervical secretion observed after mifepristone treatment. The present observation does not give any support to the hypothesis that mifepristone-induced cervical maturation is mediated via an increase in cervical prostaglandin production.