Objective: To identify and localize the receptor(s) responsible for modulating vascular effects of corticotropin-releasing factor (CRF) during pregnancy.
Methods: Reverse transcriptase-polymerase chain reaction (RT-PCR), competitive RT-PCR, and Western blot analyses were used to study the expression of CRF receptors (CRFR(1), CRFR(2alpha), and CRFR(2beta)) in the aorta and uterine vascular bed of nonpregnant and late (day 18) and term pregnant (day 22) Sprague-Dawley rats. Immunohistochemistry was done to localize the CRF receptor in the aortic wall. There were six rats in each study group.
Results: Only CRFR(2beta) was identified in the aorta and uterine vascular bed by RT-PCR and Western blot analyses. The PCR product was sequenced to confirm its identity. Competitive RT-PCR and Western blot analyses showed that expression of CRFR(2beta) is not different in late pregnancy compared with the nonpregnant but is decreased at term. Immunohistochemistry showed high expression of CRFR(2beta) on the aortic endothelial surface but low expression in the smooth-muscle layer.
Conclusion: Only CRFR(2beta) is expressed in vasculature of nonpregnant and pregnant rats and may mediate the vasorelaxant effect of CRF. This receptor is present predominantly in the vascular endothelium and to a lesser extent in the smooth muscle. The expression of CRF receptor in pregnant rat vasculature is down-regulated at term of gestation.