Pulmonary Arterial Pressure and Electrocardiograms in Broiler Chickens Infused Intravenously with L-NAME, an Inhibitor of Nitric Oxide Synthase, or Sodium Nitroprusside (SNP), a Nitric Oxide Donor

摘要

Broilers were divided at 42 to 44 days of age into a Control group (n = 30) and a Treament group (n = 30). The mean pulmonary arterial pressure (mPAP) and electrocardiogram (ECG) Leads II and aV_F were measured 1, 2, and 4 hours after an intravenous injection of 0.9% saline (Control group) or N~w-nitro-L-arginine methyl esther (L-NAME), an inhibitor of nitric oxide synthase and thus an inhibitor of endothelial nitric oxide (NO) production (Treatment group). At 1 and 2 hours but not 4 hours post-injection, L-NAME significantly increased the mPAP and the amplitudes of the ECG S and RS waves Leads II and aV_F when compared with Control values. The correlation coefficient between the mPAP and the ECG S and RS wave amplitudes for Lead II within the Treatment group were -0.848 and -0.553 at 1 hour, and -0.798 and -0.512 at. 2 hours, respectively. The corresponding coefficients for Lead aV_F were -0.735, -0.596, -0.663, and -0.724, respectively. After suitable mPAP and ECG values had been recorded at each time interval, sodium nitroprusside (SNP), which acts as a short-lived NO donor molecule, was injected intravenously via a right-cardiac catheter. Within 5 minutes after the SNP injection, the mPAP and the ECG Lead II S and RS wave amplitudes were transiently reduced to levels that, at 1 and 2 hours after L-NAME injection, did not differ from Control values. Within 10 minutes after the SNP injection, all values returned to the levels previously induced by L-NAME. These results demonstrate that L-NAME increased the myocardial contractility and PAP, whereas SNP transiently reversed the effects of L-NAME on myocardial contractility and PAP. It appears likely from these results that the pulmonary vascular endothelium releases NO that in turn reduces the pulmonary vascular resistance or attenuates myocardial contractility in broiler chickens.