Changes of vasoactive peptides and effects of inhaled nitric oxide after pneumonectomy

To clarify the role of vasoactive peptides in the physiologic response to pneumonectomy, we investigated the changes of atrial (A-type) natriuretic peptide (ANP). C-type natriuretic peptide (CNP), and endothelin-1 (ET-1) levels in the lung and blood after pneumonectomy and the effects of inhaled nitric oxide (NO; 5 ppm) after pneumonectomy in beagle dogs. The concentrations of these peptides in the lung and blood were measured by radioimmunoassay. The dogs in group A (n = 10) were observed without NO inhaling after right pneumonectomy, and the dogs in group B (n = 5) were observed with NO inhaling from 120 to 180 min after right pneumonectomy. After the thoracotomy, right lung tissue was resected for the pre-operative histological control. Tissue from the left lung was obtained at 120 min (5 dogs in group A), at 180 min (5 dogs in group A), and after 60 min of NO inhalation (group B) for the post-operative histological material. Peripheral blood was collected from the femoral artery. The pulmonary arterial pressure (PAP) was significantly increased after pneumonectomy, but rapidly decreased to the same level as the pre-operative stage after NO inhalation. Increases of plasma ANP, lung ANP and lung CNP levels occurred after pneumonectomy, while the ET-1 level was unchanged. Inhaled NO rapidly reduced the plasma ANP, lung ANP and lung CNP. These results indicate that both ANP and CNP act to maintain normotensive homeostatic balance in the pulmonary circulation.