Cervical ripening after treatment with prostaglandin E2 or antiprogestin (RU486).: Possible mechanisms in relation to gonadal steroids

Objective: To compare the mechanisms for cervical ripening after treatment with prostaglandin E-2 or antiprogestin (RU486) to spontaneous cervical ripening, with focus on gonadal steroid receptors. Study design: Cervical biopsies were obtained from postpartal women after treatment with prostaglandin E-2 (n=10), or antiprogestin (n=5). Postpartal women after spontaneous cervical ripening (n=10) served as controls. Levels of estrogen and progesterone receptors, their mRNAs, insulin-like growth factor I mRNA and serum estradiol and progesterone were quantitated. The collagen concentration and solubility by pepsin were determined. Statistical tests used were Kruskal-Wallis and Mann-Whitney U test. Results: After prostaglandin E-2 treatment the collagen concentration was higher (P<0.05) as compared to spontaneous ripening. After antiprogestin treatment the estrogen receptor concentration was higher (P<0.05) in comparison to spontaneous ripening. Conclusion: The elevated estrogen receptor concentration after antiprogestin treatment, in contrast to spontaneous ripening, and prostaglandin E-2 treatment, indicates a that a receptor-mediated progesterone withdrawal does not explain the events behind spontaneous cervical ripening at parturition. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.