Pulmonary artery endothelium-dependent vasodilation is impaired in a chicken model of pulmonary hypertension.

Among chicken strains, broilers are prone to pulmonary hypertension, whereas Leghorns are not. Relaxations to endothelium-dependent (ACh, A23187) and endothelium-independent [sodium nitroprusside (SNP), papaverine (PPV)] vasodilators were compared in preconstricted pulmonary artery (PA) rings from these chicken strains. ACh (10-7, 10-6, and 10-5 M)- and A23187 (10-6 and 10-5.5 M)-induced relaxations were smaller ( P < 0.05) in broilers than Leghorns. N G-nitro-l-arginine methyl ester (10-3.5 M) caused similar reductions in ACh-induced relaxations in both strains.l-Arginine (10-4 M) enhanced ACh-induced relaxations more in broilers than Leghorns. Relaxations to 10-10-10-6M SNP did not differ between strains, but were greater ( P < 0.05) in broilers than Leghorns at higher concentrations (10-5 and 10-4 M). PPV (10-4 M)- and SNP (10-4 M)-induced maximal relaxations were greater in broilers than in Leghorns (176.2 ± 14.7 vs. 120.9 ± 14.7% and 201.3 ± 7.8 vs. 171.2 ± 10.7%, respectively, P < 0.05). Broiler PA rings appear to have increased intrinsic tone and reduced endothelium-derived nitric oxide activity, both of which may contribute to the susceptibility of broiler chickens to pulmonary hypertension.