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

Monica Longo, MD

Mariam Ali, MS

George R. Saade, MD

Kristof Chwalisz, MD,PhD

Department of Obstetrics and Gynecology, University of Texas Medical Branch, Galveston, Texas; Research Laboratories of Schering AG, Berlin, Germany

Robert E. Garfield, PhD

Department of Obstetrics and Gynecology, University of Texas Medical Branch, Galveston, Texas; Research Laboratories of Schering AG, Berlin, Germany; Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Texas Medical Branch, 301 University Boulevard, Route J-62, Galveston, TX 77555-1062; regarfiel{at}utmb.edu

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, CRFR₂, and CRFR_2ß) 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_2ß 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_2ß is not different in late pregnancy compared with the nonpregnant but is decreased at term. Immunohistochemistry showed high expression of CRFR_2ß on the aortic endothelial surface but low expression in the smooth-muscle layer.

Conclusion: Only CRFR_2ß 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.

Key Words: Corticotropin-releasing factor receptor • pregnant rat • aorta • uterine artery • endothelium

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