Active response of pulmonary veins to distention of a single pulmonary vein in intact dogs

The effects of balloon catheter distention of a single pulmonary vein were studied in three groups of intact dogs by cardiac catheterization techniques. Distention in dogs with intact vagus nerves caused reflex pulmonary vasoconstriction characterized by an abrupt pressor response in the pulmonary artery and small pulmonary vein and caused a decrease in circulating pulmonary blood volume, without changes in cardiac output or left atrial pressure. In addition, diuresis usually followed distention of a single pulmonary vein. In another group of intact dogs, similar vascular pressor responses occurred in a single lobe, which was being pump-perfused with right atrial blood at a constant flow rate through a large balloon catheter. These vascular and diuretic responses were abolished, in other dogs, by bilateral cervical vagotomy and administration. Although distention of all pulmonary veins by partial left atrial obstruction passively dilates the pulmonary veins and increases pulmonary blood volume, these studies indicate that balloon distention of a single pulmonary vein in intact dogs actively constricts the unobstructed pulmonary veins and decreases circulating pulmonary blood volume.