Guanosine 5'-O-(3-thiotriphosphate) causes endothelium-dependent, pertussis toxin-sensitive relaxations in porcine coronary arteries. |
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Authors: | T Shibano J Codina L Birnbaumer P M Vanhoutte |
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Institution: | Center for Experimental Therapeutics, Baylor College of Medicine, Houston, TX 77030. |
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Abstract: | To determine whether direct stimulation of endothelial G-proteins causes relaxations of the underlying vascular smooth muscle, the effects of guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) and sodium fluoride were studied in porcine coronary arteries and endothelial cells. Isometric tension was measured in coronary rings contracted with prostaglandin F2 alpha. GTP gamma S (in the presence of saponin) and sodium fluoride (in the presence of AlCl3) relaxed rings with, but not those without endothelium. The responses were inhibited by nitro-L-arginine and pertussis toxin. In membrane fractions of coronary endothelial cells, GTP gamma S and sodium fluoride inhibited the ADP-ribosylation of G-proteins catalyzed with 32P]-NAD and pertussis toxin. These data suggest that direct stimulation of G-proteins in endothelial cells by GTP gamma S and sodium fluoride causes a pertussis toxin-sensitive relaxation which may be attributed to the release of nitric oxide. |
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