This Article Full Text Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Rapps, J. A. Articles by Parker, J. L. Search for Related Content PubMed PubMed Citation Articles by Rapps, J. A. Articles by Parker, J. L.

(Circulation. 1997;95:231-239.)
© 1997 American Heart Association, Inc.

Articles

Mechanisms of Altered Contractile Responses to Vasopressin and Endothelin in Canine Coronary Collateral Arteries

Julie A. Rapps, PhD; Allan W. Jones, PhD; Michael Sturek, PhD; Lawrence Magliola, PhD; Janet L. Parker, PhD

the Department of Physiology and the Dalton Cardiovascular Research Center, University of Missouri, Columbia.

Background Mature coronary collateral arteries are hyperresponsive to vasopressin; in contrast, contractile responses of collaterals to endothelin are attenuated. Our goal was to determine the cellular mechanisms underlying these differences in reactivity using two sizes of canine collateral arteries isolated from hearts subjected to chronic coronary occlusion.

Methods and Results Contractile responses to vasopressin (100 nmol/L) were enhanced threefold to fourfold in near-resistance (200 µm lumen diameter) and conduit (500 µm lumen diameter) collateral arteries compared with similarly sized noncollateral coronary arteries (P<.01). In contrast, contractions of both sizes of collaterals in response to endothelin (0.01 to 30 nmol/L) were smaller than responses of size-matched noncollateral arteries (P<.05). Pretreatment with either indomethacin (5 µmol/L), a cyclooxygenase inhibitor, or N^G-nitro-L-arginine methyl ester (100 µmol/L), a nitric oxide synthase inhibitor, did not alter the relative responsiveness of collateral arteries to vasopressin or endothelin compared with noncollateral arteries. Vasopressin produced greater increases of intracellular free Ca²⁺ (measured by use of fura-2 microfluorometry and Ca²⁺-dependent ⁴²K⁺ efflux) in smooth muscle of collateral arteries than in smooth muscle of noncollateral arteries (P<.05). Surprisingly, endothelin-induced increases of Ca²⁺ were not different in smooth muscle of collateral and noncollateral arteries (P>.05).

Conclusions We conclude that altered contractile responsiveness of collateral arteries to vasopressin and endothelin does not result from altered synthesis/release of nitric oxide or prostaglandins. Parallel enhancement of vasopressin-mediated Ca²⁺ and contractile responses suggests increases in vasopressin receptor number, affinity, and/or efficiency of coupling mechanisms in collateral smooth muscle. The dissociation between endothelin-induced contractile and Ca²⁺ responses of collaterals indicates that the mechanisms involved in increasing Ca²⁺ sensitivity of contractile proteins during endothelin stimulation may be altered in collateral arteries.

Key Words: vasopressin • endothelin • muscle, smooth • calcium

This article has been cited by other articles:

				C. L. Heaps, M. L. Mattox, K. A. Kelly, C. J. Meininger, and J. L. Parker Exercise training increases basal tone in arterioles distal to chronic coronary occlusion Am J Physiol Heart Circ Physiol, March 1, 2006; 290(3): H1128 - H1135. [Abstract] [Full Text] [PDF]

				E. S. Antezano and M. Hong Sudden Cardiac Death J Intensive Care Med, November 1, 2003; 18(6): 313 - 329. [Abstract] [PDF]

				J. L. Dixon, J. D. Stoops, J. L. Parker, M. H. Laughlin, G. A. Weisman, and M. Sturek Dyslipidemia and Vascular Dysfunction in Diabetic Pigs Fed an Atherogenic Diet Arterioscler Thromb Vasc Biol, December 1, 1999; 19(12): 2981 - 2992. [Abstract] [Full Text] [PDF]

				J. A. Rapps, P. R. Myers, Q. Zhong, and J. L. Parker Development of Endothelium-Dependent Relaxation in Canine Coronary Collateral Arteries Circulation, October 20, 1998; 98(16): 1675 - 1683. [Abstract] [Full Text] [PDF]

				J. A. Rapps, M. Sturek, A. W. Jones, and J. L. Parker Altered reactivity of coronary arteries located distal to a chronic coronary occlusion Am J Physiol Heart Circ Physiol, October 1, 1997; 273(4): H1879 - H1887. [Abstract] [Full Text] [PDF]