RELAXATION OF INTRAPULMONARY ARTERY AND VEIN BY NITROGEN-OXIDE CONTAINING VASODILATORS AND CYCLIC-GMP

  • 1 January 1984
    • journal article
    • research article
    • Vol. 228  (1) , 33-42
Abstract
The relationship between tissue cyclic nucleotide levels and relaxation of bovine intrapulmonary arterial and venous smooth muscle in response to nitroglycerin, nitroprusside, S-nitroso-N-acetylpenicillamine and isoproterenol was studied. cGMP may be involved in the relaxation of vascular smooth muscle produced by nitrogen oxide-containing vasodilators and S-nitrosothiols may act as intermediates of the latter agents. Nitroglycerin, nitroprusside and S-nitroso-N-acetylpenicillamine were more potent as relaxants of venous than arterial segments. Each agent elevated tissue cGMP levels, but not cAMP levels, before relaxation. These nitrogen oxide-containing agents were more potent as elevators of cGMP levels in venous than arterial tissue and this correlated generally with their effects on vascular smooth muscle tone. Methylene blue antagonized both relaxation and increased cGMP levels elicited by nitroglycerin, nitroprusside and S-nitroso-N-acetylpenicillamine. 8-Bromo-cGMP was equally effective in reducing induced tone in arterial or venous segments. Isoproterenol relaxed arterial and venous segments with equivalent sensitivities. Relaxation by isoproterenol was preceded by or occurred concomitantly with increased levels of cAMP but not cGMP and both effects were antagonized by propranolol. Vascular smooth muscle relaxation in response to nitrogen oxide-containing vasodilators or isoproterenol may be mediated or modulated by the intracellular accumulation of cGMP or cAMP, respectively.