DISSOCIATION IN THE CONTROL OF CERVICAL EOSINOPHILIC INFILTRATION ANDCOLLAGENOLYSIS AT THE END OF PREGNANCY OR AFTER PSEUDOPREGNANCY IN OVARIECTOMIZED STEROID-TREATED RATS

Previous studies have demonstrated that during parturition the physiol ogical ripening that permits dilation of the cervical canal is doe to a widespread collagenolysis that follows a heavy polymorphonuclear leu kocyte invasion of the uterine cervix, The aim of this study was to in vestigate whether there is any association between the ovarian steroid hormones involved in rat parturition and this phenomenon, Pregnant or pseudopregnant rats were ovariectomized (OVX) at Day 9 and then given a hormonal treatment (sufficient to maintain fetal viability) until D ay 23. Cervical biopsies, taken from animals killed intrapartum or 1 h before expected parturition, were studied for eosinophilic infiltrati on and collagen birefringence. Intrapartum or sham-OVX pregnant rats s howed a massive eosinophilic infiltration and a widespread collagenoly sis as indicated by a loss of collagen birefringence, Ovariectomized p regnant rats treated with estrogen plus progesterone or with progester one alone showed neither infiltration nor collagenolysis. In rats OVX during pseudopregnancy, estrogen given alone induced a significant inf iltration of eosinophils in the cervical stroma; however, treatment wi th the combination of estrogen and progesterone was not able to promot e eosinophilic infiltration. Collagenolysis was absent in all pseudopr egnant animals, These results show that estrogen induced a cervical eo sinophilic infiltration in rats but that when progesterone was added t o the estrogen treatment the infiltration was not present; in addition , none of the steroid hormones assessed were responsible for the colla genolysis found in the cervical tissue at term.