HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 289/2/H792    most recent 00050.2005v1 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 Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by Kim, M. Y. Articles by Suh, S. H. Search for Related Content PubMed PubMed Citation Articles by Kim, M. Y. Articles by Suh, S. H.

Contribution of Na⁺-K⁺ pump and K_IR currents to extracellular pH-dependent changes of contractility in rat superior mesenteric artery

¹Department of Physiology and Medical Research Institute and ²Department of Internal Medicine, College of Medicine, Ewha Women's University, Seoul, Republic of Korea

Submitted 18 January 2005 ; accepted in final form 13 April 2005

We compared the branches and trunk of rat superior mesenteric artery (SMA) with respect to extracellular pH (pH_o)-dependent changes in vascular contractility. Decreases in pH_o from 7.8 to 6.4 significantly reduced apparent affinity (pD₂) to norepinephrine (NE) and maximal contraction by NE, which were more prominent in larger-diameter arteries. On the other hand, decreases in pH_o significantly reduced Ba²⁺-sensitive K⁺-induced relaxation (which was evoked by elevation of extracellular K⁺ concentration from 6 to 12 mM) in the first branch and inhibited inwardly rectifying K⁺ (K_IR) currents in cultured smooth muscle cells (SMCs) of SMA. RT-PCR revealed transcripts for Kir2.1 in the SMCs. Real-time PCR analysis revealed 6.1-, 3.3-, and 2.2-fold increases in the Kir2.1 mRNA-to--actin mRNA ratios of SMCs of the third, second, and first branches, respectively, vs. the corresponding relative levels of trunk SMCs. The magnitudes of K⁺-induced relaxation were significantly greater in smaller-diameter arteries, and there was a strong correlation between the transcript levels of Kir2.1 and K⁺-induced relaxation. A decrease in pH_o reduced ouabain-sensitive K⁺-induced relaxation and ouabain-induced contraction. A decrease in pH_o from 7.4 to 6.4 depolarized membrane potential of the cultured SMCs. From these results, we conclude that an increase in pH_o activates K_IR currents and the Na⁺-K⁺ pump, which then reduces vascular contractility. Inasmuch as K_IR channel densities are significantly greater in smaller-diameter arteries, the reduction in vascular contractility on increasing pH_o is more pronounced in smaller-diameter arteries.

inwardly rectifying K⁺ current; vascular contractility; potassium channels; smooth muscle cells

This article has been cited by other articles:

				S. Wang, Y. Zhang, W. G. Wier, X. Yu, M. Zhao, H. Hu, L. Sun, X. He, Y. Wang, B. Wang, et al. Role of store-operated Ca2+ entry in adenosine-induced vasodilatation of rat small mesenteric artery Am J Physiol Heart Circ Physiol, July 1, 2009; 297(1): H347 - H354. [Abstract] [Full Text] [PDF]

				F. J. Haddy, P. M. Vanhoutte, and M. Feletou Role of potassium in regulating blood flow and blood pressure Am J Physiol Regulatory Integrative Comp Physiol, March 1, 2006; 290(3): R546 - R552. [Abstract] [Full Text] [PDF]

				M. Y. Kim, G. H. Seol, G. H. Liang, J. A. Kim, and S. H. Suh Na+-K+ pump activation inhibits endothelium-dependent relaxation by activating the forward mode of Na+/Ca2+ exchanger in mouse aorta Am J Physiol Heart Circ Physiol, November 1, 2005; 289(5): H2020 - H2029. [Abstract] [Full Text] [PDF]