Misoprostol induces cervical nitric oxide release in pregnant, but not in nonpregnant, women

Objective The cells of the human uterine cervix synthesize nitric oxide, which may be a factor in cervical ripening. We studied the effect of misoprostol on cervical nitric oxide release in nonpregnant and pregnant women. Study design Seventy-two nonpregnant (n = 15) and pregnant (n = 57; 26 in early pregnancy, 31 in late pregnancy) women were treated with either vaginal misoprostol (n = 54) or vaginal placebo (n = 18). The dose of misoprostol was 400 μg in nonpregnant and early pregnancy group, and 25 μg in late pregnancy group. Serial cervical fluid samples, collected before and up to 3 hours after misoprostol/placebo, were assessed for the concentration of nitric oxide metabolites by means of the Griess reaction. Results Placebo had no effect on cervical fluid nitric oxide metabolite level. In 1 to 3 hours, misoprostol induced 4.3- to 5.2-fold elevations in cervical fluid Nox concentrations in early pregnancy (P< .01), and 4.4- to 18.2-fold elevations in late pregnancy (P< .01), but these responses did not differ significantly from each other. Misoprostol had no effect on cervical fluid nitric oxide metabolites in nonpregnant women. There was a trend towards a relationship between cervical nitric oxide stimulation after misoprostol and cervical ripening. Conclusion Vaginal misoprostol stimulates cervical nitric oxide release in pregnancy. This suggests a joint action of nitric oxide and prostaglandins in cervical ripening