des-Arg9-bradykinin produces tone-dependent kinin B1 receptor-mediated responses in the pulmonary vascular bed.

Responses to des-Arg9-bradykinin, a selective kinin B1 receptor agonist, were characterized in the pulmonary vascular bed of the intact-chest cat. Injections of des-Arg9-bradykinin into the perfused lobar artery under low-resting tone conditions caused dose-related increases in lobar arterial pressure; whereas in the same experiment under elevated tone conditions, injections of the B1 agonist caused dose-related decreases in lobar arterial pressure. Vasoconstrictor responses to des-Arg9-bradykinin under low-tone conditions and vasodilator responses under elevated-tone conditions were antagonized by des-Arg9,[Leu8]-bradykinin, a kinin B1 receptor antagonist, whereas responses under low- and high-tone conditions were not altered by Hoe 140, a kinin B2 receptor antagonist. Vasoconstrictor responses to des-Arg9-bradykinin under low-tone conditions were attenuated by phentolamine, prazosin, and reserpine but not by sodium meclofenamate, suggesting that release of catecholamines and activation of alpha-adrenergic receptors are involved. Pulmonary vasodilator responses under elevated-tone conditions were inhibited by N omega-nitro-L-arginine methyl ester, suggesting that des-Arg9-bradykinin stimulates the release of nitric oxide, whereas meclofenamate and U-37883A, a nonsulfonylurea ATP-sensitive K+ channel antagonist, did not alter vasodilator responses to the B1 receptor agonist. These results suggest that vasoconstrictor responses to des-Arg9-bradykinin under low-tone conditions are mediated by the activation of kinin B1 receptors, the release of catecholamines within the lung, and the activation of alpha-adrenergic receptors, whereas vasodilator responses under elevated tone conditions are mediated by activation of B1 receptors and the release of nitric oxide from the endothelium.(ABSTRACT TRUNCATED AT 250 WORDS)