Journal
CANADIAN JOURNAL OF PHYSIOLOGY AND PHARMACOLOGY
Volume 96, Issue 8, Pages 839-844Publisher
CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS
DOI: 10.1139/cjpp-2017-0557
Keywords
calcium-activated potassium channel; endothelium-dependent hyperpolarization; hypertension; superior mesenteric artery; SHR
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Funding
- JSPS KAKENHI [JP17K08318, JP15K07975]
- Suzuken Memorial Foundation
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The purpose of this study was to determine the relationship of K-Ca channels to endothelium-dependent hyperpolarizing factor (EDHF)-mediated relaxation induced by acetylcholine (ACh) in the superior mesenteric arteries of 7-month-old spontaneously hypertensive rats (SHR). Upon inhibition of nitric oxide synthase and cyclooxygenase, ACh-induced EDHF-mediated relaxation was found to be weaker in SHR than in age-matched Wistar Kyoto rats (WKY). These relaxations in both group were attenuated by combined treatment with small-conductance and intermediate-conductance Ca2+-activated K+ channels (SKCa and IKCa) inhibitors, with the exception of relaxation resistant to inhibition of these channels in SHR (vs. WKY). Treatment with large-conductance Ca2+-activated K+ channels (BKCa) inhibitor specifically attenuated relaxation in SHR, but not in WKY. Protein expression of IKCa and SKCa in the arteries did not differ between the 2 groups, whereas ratio of slo beta 1 subunit to alpha subunit of BKCa was increased in SHR (vs. WKY). These results suggest that EDHF-mediated relaxations in superior mesenteric arteries are impaired in SHR, and utilize components of BKCa in addition to SKCa/IKCa channel activities, that the increased participation of BKCa may be attributable to alterations in alpha and slo beta 1 subunit ratio, and that components unrelated to K-Ca activity may also contribute to the difference between SHR and WKY arteries.
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