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Am J Physiol Lung Cell Mol Physiol 293 (2): 472-479

Copyright © 2007 by the American Physiological Society.

Vasoconstrictor effect of endothelin-1 on hypertensive pulmonary arterial smooth muscle involves Rho-kinase and protein kinase C

Scott A. Barman

Department of Pharmacology and Toxicology, Medical College of Georgia, Augusta, Georgia

Received for publication 20 March 2006. Accepted for publication 22 April 2007.

Abstract: Although one of the common characteristics of pulmonary hypertension is abnormal sustained vasoconstriction, the signaling pathways that mediate this heightened pulmonary vascular response are still not well defined. Protein kinase C (PKC) and Rho-kinase are regulators of smooth muscle contraction induced by G protein-coupled receptor agonists including endothelin-1 (ET-1), which has been implicated as a signaling pathway in pulmonary hypertension. Toward this end, it was hypothesized that both Rho-kinase and PKC mediate the pulmonary vascular response to ET-1 in hypertensive pulmonary arterial smooth muscle, and therefore, the purpose of this study was to determine the role of PKC and Rho-kinase signaling in ET-1-induced vasoconstriction in both normotensive (Sprague-Dawley) and hypertensive (Fawn-Hooded) rat pulmonary arterial smooth muscle. Results indicate that ET-1 caused greater vasoconstriction in hypertensive pulmonary arteries compared with the normal vessels, and treatment with the PKC antagonists chelerythrine, rottlerin, and Gö 6983 inhibited the vasoconstrictor response to ET-1 in the hypertensive vessels. In addition, the specific Rho-kinase inhibitor Y-27632 significantly attenuated the effect of ET-1 in both normotensive and hypertensive phenotypes, with greater inhibition occurring in the hypertensive arteries. Furthermore, Western blot analysis revealed that ET-1 increased RhoA expression in both normotensive and hypertensive pulmonary arteries, with expression being greater in the hypertensive state. These results suggest that both PKC and Rho/Rho-kinase mediate the heightened pulmonary vascular response to ET-1 in hypertensive pulmonary arterial smooth muscle.

Key Words: pulmonary hypertension • abnormal sustained vasoconstriction

Address for reprint requests and other correspondence: S. A. Barman, Dept. of Pharmacology and Toxicology, Medical College of Georgia, Augusta, GA 30912 (e-mail: sbarman{at}mcg.edu)

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