Isosorbide mononitrate induces increased cervical expression of cyclooxygenase-2, but not of cyclooxygenase-1, at term.

Abstract Objective Prostaglandin and nitric oxide (NO) are both known to be involved in cervical ripening at term. The aim of the study was to investigate if NO has an effect on cervical expression of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2), the two main isoenzymes involved in prostaglandin synthesis, and to localize these enzymes within the cervix. Study design Women with an unripe cervix scheduled for elective caesarean section at term were randomly selected to receive vaginally either the NO donor isosorbide mononitrate (IMN) or placebo 4 h before surgery. At the operating theatre, cervical tissue specimens were obtained for immunoblotting and immunohistochemistry. Results Increased expression of COX-2 was found in specimens exposed to IMN compared to specimens obtained from women in the placebo group. There was no difference in the expression of COX-1. Immunohistochemistry revealed similar localization of the two enzymes in treated and untreated women. Conclusions Vaginal administration of IMN induces increased cervical expression of COX-2, but not of COX-1. This pathway may be of importance in the process of cervical ripening at term.