Structural Changes and Effect of Denopamine on Alveolar Fluid Clearance in Hypoxic Rat Lungs

Terbutaline (beta(2)-adrenergic agonist) can increase alveolar fluid clearance (AFC) under physiologic and pathologic conditions. It is unknown whether beta(1)-adrenergic agonists also increase AFC under pathologic conditions. The aim of this study was to investigate the effect of denopamine (beta(1)-adrenergic agonist) on AFC in hypoxic lung injury and the possible mechanisms involved. Hypoxic rats were exposed to 10% oxygen. 10(-5) mol/L denopamine alone or combined with beta receptor antagonists, Na+ channel blocker, or Na+/K+-ATPase blocker were perfused into the alveolar space of rats exposed to 10% oxygen for 48 h. AFC and total lung water content (TLW) were measured. AFC did not change for the first 24 h but then decreased after 48h exposure to 10% oxygen. The perfusion of denopamine significantly increased AFC in normoxic and hypoxic rats. The AFC-stimulating effect of denopamine lowered with amiloride (a Na+ channel blocker) and ouabain (a Na+/K+-ATPase inhibitor) by 35 and 53%, respectively. Colchicine significantly inhibited the effect of denopamine. Denopamine can increase the AFC during hypoxic lung injury in rats and accelerate the absorption of pulmonary edema.