Abstract
Experiments were designed to determine the effect of gap junction inhibitors on endothelium-dependent contractions. Isolated aortic rings of spontaneously hypertensive rats (SHR) were suspended in vitro for isometric force recording. The nonselective gap junction inhibitor, carbenoxolone, reduced endothelium-dependent contractions to acetylcholine and the calcium ionophore A23187 [5-methylamino-2-(2S,3R,5R,8S,9S)-3,5,9-trimethyl-2-(1-oxo-(1H-pyrrol-2-yl)propan-2-yl)-1,7-dioxaspiro-(5,5)undecan-8-yl)methyl)benzooxazole-4-carboxylic acid]. There was no or modest effect of the gap peptides 40Gap27, 37,43Gap27, or 43Gap26 when applied alone on endothelium-dependent contractions. However, the combined treatment with the three gap peptides significantly decreased endothelium-dependent contractions. The combined inhibition of the three connexins was not as effective as carbenoxolone, suggesting the involvement of other connexins in the process of endothelium-dependent contraction. The present study shows the involvement of gap junctions in endothelium-dependent contractions of the SHR aorta, presumably that of the combination of connexins 37, 40, and 43 rather than a single subtype of these proteins. Contractions of the vascular smooth muscle caused by 9,11-dideoxy-11α, 9α-epoxymethanoprostaglandin F2α (U46619) and prostacyclin, but not to those of endoperoxides and phenylephrine, were reduced only minimally by carbenoxolone. Thus, if gap junction signaling is involved in the contraction of the vascular smooth muscle to thromboxane-prostanoid receptor agonists, their contribution is small. This suggests that the reduction of endothelium-dependent contractions by carbenoxolone and the gap peptides cannot be attributed to the homocellular gap junctions between vascular smooth muscle, but is more likely to involve the homocellular gap junctions between endothelial cells and/or myoendothelial gap junctions.
Footnotes
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This work was supported by a Competitive Earmarked Research Grant of the Research Grant Council of Hong Kong and by the Centre for Healthy Aging of the University of Hong Kong.
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.108.140046.
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ABBREVIATIONS: ROS, reactive oxygen species; SHR, spontaneously hypertensive rat; WKY, Wistar-Kyoto rat; TP, thromboxane prostanoid; COX, cyclooxygenase; NS-398, N-[2-(cyclohexyloxy)-4-nitrophenyl]methanesulfonamide; EDCF, endothelium-derived contracting factor; SOD, superoxide dismutase; DETCA, diethyldithiocarbamate acid; Cx, connexin; PE, phenylephrine; U46619, 9,11-dideoxy-11α, 9α-epoxymethanoprostaglandin F2α; A23187, 5-methylamino-2-(2S,3R,5R,8S,9S)-3,5,9-trimethyl-2-(1-oxo-1-(1H-pyrrol-2-yl)propan-2-yl)-1,7-dioxaspiro(5,5)undecan-8-yl)methyl)benzooxazole-4-carboxylic acid; 1P, prostaglandin I2.
- Received April 14, 2008.
- Accepted July 16, 2008.
- The American Society for Pharmacology and Experimental Therapeutics
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