Expression of Receptors for Corticotropin-Releasing Factor in the Vasculature of Pregnant Rats

Abstract

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 (CRFR₁, CRFR_2α, and CRFR_2β) 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_2β 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_2β is not different in late pregnancy compared with the nonpregnant but is decreased at term. Immunohistochemistry showed high expression of CRFR_2β on the aortic endothelial surface but low expression in the smooth-muscle layer.

Conclusion: Only CRFR_2β 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.