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

Title
Contribution of Na+-K+ pump and KIR currents to extracellular pH-dependent changes of contractility in rat superior mesenteric artery
Authors
Kim M.Y.Liang G.H.Kim J.A.Park S.H.Hah J.S.Suh S.H.
Ewha Authors
하종식서석효박성훈
SCOPUS Author ID
하종식scopus; 서석효scopus; 박성훈scopus
Issue Date
2005
Journal Title
American Journal of Physiology - Heart and Circulatory Physiology
ISSN
0363-6135JCR Link
Citation
vol. 289, no. 2 58-2, pp. H792 - H800
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
We compared the branches and trunk of rat superior mesenteric artery (SMA) with respect to extracellular pH (pHo)-dependent changes in vascular contractility. Decreases in pHo 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 pHo significantly reduced Ba 2+-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+ (KIR) 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-β-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 pHo reduced ouabain-sensitive K+-induced relaxation and ouabain-induced contraction. A decrease in pHo from 7.4 to 6.4 depolarized membrane potential of the cultured SMCs. From these results, we conclude that an increase in pHo activates KIR currents and the Na +-K+ pump, which then reduces vascular contractility. Inasmuch as KIR channel densities are significantly greater in smaller-diameter arteries, the reduction in vascular contractility on increasing pHo is more pronounced in smaller-diameter arteries. Copyright © 2005 the American Physiological Society.
DOI
10.1152/ajpheart.00050.2005
Appears in Collections:
의학전문대학원 > 의학과 > Journal papers
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