CORTICOTROPIN-RELEASING HORMONE-RECEPTOR SUBTYPE 1 IS SIGNIFICANTLY UP-REGULATED AT THE TIME OF LABOR IN THE HUMAN MYOMETRIUM

Circulating concentrations of CRH rise late in human pregnancy, reachi ng a peak at labor. The presence of functional CRH receptors, CRH-R1 a nd CRH-RP, in the human myometrium suggests that CRH may modulate uter ine activity. We hypothesized that the number of CRH receptors would b e higher in myometrium than fetal membranes (FM) and would change duri ng labor. Myometrial samples were collected from the lower segment (LS ) in nonpregnant, preterm (32 +/- 2 weeks), and term (39 +/- 1.6 weeks ) pregnant patients before and at labor. Fundus and LS samples were al so collected from nonpregnant, pregnant, laboring, and postpartum wome n. FM were collected at term and at labor. We identified CRH receptors in myometrium and FM by semiquantitative RT-PCR and immunohistochemis try. CRH-R1 messenger ribonucleic acid (mRNA) in the LS was decreased in pregnancy and increased significantly in both preterm and term labo r (P < 0.05), but remained unchanged in the fundus. CRH-RB mRNA was pr esent in 28% of LS myometrium with no change at labor. CRH-R1 and CRH- RI protein was localized to myometrial smooth muscle in nonpregnant an d laboring patients, with lower levels at term. CRH-R1 mRNA was presen t in chorion and decidua, but CRH-RP was undetectable in these tissues . We conclude that CRH-R1 is expressed preferentially in myometrium an d FM. Changes in CRH receptors during labor are consistent with CRH me diating effects on myometrial activity.