POSSIBLE ROLE FOR CYCLIC-GMP IN ENDOTHELIUM-DEPENDENT RELAXATION OF RABBIT AORTA BY ACETYLCHOLINE - COMPARISON WITH NITROGLYCERIN

  • 1 January 1983
    • journal article
    • research article
    • Vol. 41  (3) , 369-381
Abstract
A possible role for cGMP as a mediator of the endothelium-dependent relaxation of rabbit aorta by acetylcholine was investigated using rabbit aortic rings with and without intact endothelium. In the presence of intact endothelial cells, acetylcholine caused marked increases in tissue levels of cGMP accompanied by relaxation of the muscles. In aortic rings from which the endothelium was removed, acetylcholine caused neither cGMP elevation nor relaxation of the muscles. Acetylcholine-induced relaxation and cGMP elevation in preparations with intact endothelium were both blocked by atropine. Reasonably good temporal and dose-response correlations between cGMP elevation and relaxation were obtained with acetylcholine. Although a causal relationship was not definitely established, cGMP may mediate the endothelium-dependent relaxation of rabbit aorta by acetylcholine. In contrast to the results with acetylcholine, elevation of cGMP and relaxation of aortic rings by nitroglycerin were not dependent on the presence of endothelial cells. Lower doses of nitroglycerin relaxed the muscles without elevating cGMP levels. At higher concentrations of nitroglycerin, greater relaxation was obtained for a given degree of cGMP elevation than was the case with acetylcholine. Apparently, at least part of nitroglycerin''s relaxant effect in this tissue is independent of cGMP elevation.

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