Cyclic nucleotide interactions involved in endothelium-dependent dilatation in rat aortic rings.

Abstract

The role of cyclic nucleotides in the dilation of rat aortic rings induced by isoprenaline was studied by measuring changes in isometric tension and in cyclic nucleotide levels in rings preconstricted with phenylephrine or U46619. Isoprenaline produced significantly greater relaxation in endothelium-containing than in endothelium-denuded rings. Relaxation of endothelium-containing rings to isoprenaline was markedly inhibited by pretreating the rings with methylene blue (30 microM) or haemoglobin (10 microM). Basal cyclic-AMP levels were not affected by the presence of endothelium in the rings, but basal cyclic-GMP levels were 5-6-fold higher in endothelium-containing rings. Isoprenaline (1 m..