Nitric oxide induced cervical ripening in the human: Involvement of cyclic guanosine monophosphate, prostaglandin F2α, and prostaglandin E2

Objective: The purpose of the study was to investigate possible mechanisms and morphologic changes involved in nitric oxide–induced cervical ripening. Study design: Women scheduled for surgical termination of first trimester pregnancy were randomized to 1 of 3 groups: isosorbide 5-mononitrate 40 mg 4 hours or 10 hours before the operation or no preoperative treatment. Cervical specimens were obtained for the analysis of tissue levels of cyclic guanosine monophosphate, cyclic adenosine monophosphate, cyclo-oxygenase 1, cyclo-oxygenase 2, prostaglandin F2α, and prostaglandin E2 or were fixed in glutaraldehyde for microscopy. Results: Increased levels of cyclic guanosine monophosphate, cyclo-oxygenase 2, prostaglandin F2α, and prostaglandin E2 were found in samples that were exposed to isosorbide 5-mononitrate compared with control samples. Electron microscopy revealed stromal edema and collagen disorganization after isosorbide 5-mononitrate treatment. Conclusion: Cyclic guanosine monophosphate, prostaglandin F2α, and prostaglandin E2 are involved in nitric oxide–induced cervical ripening. Nitric oxide causes morphologic changes similar to those changes seen during spontaneous cervical ripening. (Am J Obstet Gynecol 2002;186:•745-50.)