Comparison of endothelium-dependent relaxation in bovine intrapulmonary artery and vein by acetylcholine and A23187.

This study was conducted to compare the influence of endothelium on mechanical responses of bovine intrapulmonary artery and vein to acetylcholine (ACh) and A23187 and to determine if a relationship exists between the responses and cyclic GMP (cGMP) accumulation. ACh and A23187 induced relaxation in artery and A23187 induced relaxation in vein. The relaxant responses in both vessels were abolished by rubbing the intimal surfaces, indicating that the relaxant responses depended upon the presence of a functionally intact endothelium. cGMP accumulation was temporally associated with both ACh- and A23187-induced endothelium-dependent relaxation. Both the relaxant responses and the accompanying cGMP accumulations were abolished or reduced markedly by intimal rubbing or pretreatment with methylene blue. Atropine abolished relaxation and cGMP accumulation induced by ACh in artery, but not relaxation and cGMP accumulation induced by A23187. Whereas indomethacin did not affect either ACh- or A23187-induced relaxation in artery, it slightly, but significantly, reduced A23187-induced relaxation in vein. In contrast to its effect in artery, ACh only induced contractile responses in vein and did not alter cGMP levels, whether or not functional venous endothelium was present. However, ACh did relax veins when arterial endothelium was present in crossover experiments using a modified sandwich technique. At concentrations which induced endothelium-dependent relaxation in artery, ACh similarly induced no, or only minimal, contraction in both artery and vein in which endothelium was functionally destroyed. These findings demonstrate that bovine intrapulmonary artery and vein exhibit endothelium-dependent relaxation in response to A23187, and similar to ACh-induced relaxation in the artery, A23187-induced relaxation is associated closely with accumulation of cGMP.(ABSTRACT TRUNCATED AT 250 WORDS)