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Mesenteric Arterial Relaxation to Calcitonin Gene-Related Peptide Is Increased During Pregnancy and by Sex Steroid Hormones¹

Departments of Obstetrics & Gynecology,⁴ Anatomy & Neuroscience,⁵ Internal Medicine,⁶ The University of Texas Medical Branch, Galveston, Texas 77555 Cardiovascular Disease Research Program,⁷ Julius L. Chambers Biomedical Biotechnology Research Institute, North Carolina Central University, Durham, North Carolina 27707

The present study investigated whether pregnancy and circulatory ovarian hormones increase the sensitivity of the mesenteric artery to calcitonin gene-related peptide (CGRP)-induced relaxation and possible mechanisms involved in this process. Mesenteric arteries from young adult male rats or female rats (during estrous cycle, after ovariectomy, at Day 20 of gestation, or Postpartum Day 2) were isolated, and the responsiveness of the vessels to CGRP was examined with a small vessel myograph. The CGRP (10^–10 to 10^–7 M) produced a concentration-dependent relaxation of norepinephrine-induced contractions in mesenteric arteries of all groups. Arterial relaxation sensitivity to CGRP was significantly (P < 0.05) greater in female rats compared with male rats. Pregnancy increased the sensitivity to CGRP significantly (P < 0.05) compared to ovariectomized and Postpartum Day 2 rats. In pregnant rats, CGRP-receptor antagonist, CGRP_8–37, inhibited the relaxation responses produced by CGRP. The CGRP-induced relaxation was not affected by N^G-nitro-L-arginine methyl ester (nitric oxide inhibitor, 10^–4 M) but was significantly (P < 0.05) attenuated by an inhibitor of guanylate cyclase (1H-[1 , 2 , 4 ]oxadizaolo[4 , 3 -a]quinoxalin-1-one, 10^–5 M). Relaxation responses of CGRP on mesenteric arteries were blocked (P < 0.05) by a cAMP-dependent protein kinase A inhibitor, Rp-cAMPs (10^–5 M). The CGRP-induced vasorelaxation was significantly (P < 0.05) attenuated by calcium-dependent (tetraethylammonium, 10^–3 M), but not ATP-sensitive (glybenclamide, 10^–5 M), potassium channel blocker. Therefore, the results of the present study suggest that mesenteric vascular sensitivity to CGRP is higher during pregnancy and that cAMP, cGMP, and calcium-dependent potassium channels appear to be involved. Therefore, we propose that CGRP-mediated vasodilation may be important to maintain vascular adaptations during pregnancy.

¹ Supported by the following National Institutes of Health (NIH) grants: HL 58144, HD 40828, and HL 72650.

² Correspondence: Chandrasekhar Yallampalli, Department of Obstetrics & Gynecology, The University of Texas Medical Branch, 301 University Boulevard, Route 1062, Galveston, TX 77555-1062. FAX: 409 747 0475; chyallam{at}utmb.edu

³ Deceased

This article has been cited by other articles:

				A. M. Aukes, N. Bishop, J. Godfrey, and M. J. Cipolla The Influence of Pregnancy and Gender on Perivascular Innervation of Rat Posterior Cerebral Arteries Reproductive Sciences, April 1, 2008; 15(4): 411 - 419. [Abstract] [PDF]

				M. Chauhan, G. R. Ross, U. Yallampalli, and C. Yallampalli Adrenomedullin-2, a Novel Calcitonin/Calcitonin-Gene-Related Peptide Family Peptide, Relaxes Rat Mesenteric Artery: Influence of Pregnancy Endocrinology, April 1, 2007; 148(4): 1727 - 1735. [Abstract] [Full Text] [PDF]

				G. R. Ross, M. Chauhan, P. R. Gangula, L. Reed, C. Thota, and C. Yallampalli Female Sex Steroids Increase Adrenomedullin-Induced Vasodilation by Increasing the Expression of Adrenomedullin2 Receptor Components in Rat Mesenteric Artery Endocrinology, January 1, 2006; 147(1): 389 - 396. [Abstract] [Full Text] [PDF]