The expression of EP3-6 and inducible nitric oxide synthase messenger RNA are correlated in pregnant and misoprostol-treated but not in nongravid or menopausal myometrium

Objective: Our purpose was to investigate the expression level of inducible nitric oxide synthase (iNOS) in nongravid and gravid human myometrium and assess its relation to the expression of EP3 prostaglandin receptor isoforms. Study Design: Myometrial tissue from a cohort of gravid, nongravid, and menopausal subjects and from nongravid subjects exposed to misoprostol was obtained and analyzed for iNOS messenger RNA (mRNA) expression and compared with previously determined mRNA levels for the EP3-6 prostaglandin receptor from the same samples by means of semiquantitative polymerase chain reaction. Results: Significantly higher levels of iNOS mRNA expression were found in the gravid compared with premenopausal nongravid (P < .02) and menopausal (P < .05,) samples. Linear regression analysis of iNOS versus EP3-6 expression showed a positive correlation between all studied samples (n = 47, P < .0001, r = 0.815). Among individual groups, a significant linear correlation was found only in pregnant (n = 10, P < .0001, r = 0.785) and misoprostol-exposed (n = 7, P = .0256, r = 0.815) subjects. No correlation between iNOS and EP3-6 mRNA levels was noted in the nongravid premenopausal groups (n = 10, P = .205, r = 0.350), although a nonsignificant trend was found for the menopausal group (n = 10, P = .0535, r = 0.624). When the data from pregnant patients were stratified, both laboring and nonlaboring women displayed the observed correlation (n = 6, P < .0001, r = 0.993; and N = 13, P = .008, r = 0.697, respectively). Conclusion: iNOS and EP3-6 expression are strongly correlated in gravid and misoprostol-treated, nongravid myometrium. (Am J Obstet Gynecol 2002;186:1202-6.)