Catecholamines increase lung edema clearance in rats with increased left atrial pressure

Catecholamines increase lung edema clearance in rats with increased left at rial pressure. J Appl Physiol 90: 1088-1094, 2001.-During hydrostatic pulmo nary edema, active Na+ transport and alveolar fluid reabsorption are decrea sed. Dopamine (DA) and isoproterenol (ISO) have been shown to increase acti ve Na+ transport in rat lungs by upregulating Na+-K+-ATPase in the alveolar epithelium. We studied the effects of DA and ISO in isolated rat lungs wit h increased left atrial pressure (Pla = 15 cmH(2)O) compared with control r ats with normal Pla (Pla = 0). Alveolar fluid reabsorption decreased from c ontrol value of 0.51 +/- 0.02 to 0.27 +/- 0.02 ml/h when Pla was increased to 15 cmH(2)O (P < 0.001). DA and ISO increased the alveolar fluid reabsorp tion back to control levels. Treatment with the D-1 antagonist SCH-23390 in hibited the stimulatory effects of DA (0.30 +/- 0.02 ml/h), whereas fenoldo pam, a specific D-1- receptor agonist, increased alveolar fluid reabsorptio n in rats exposed to Pla of 15 cmH(2)O (0.47 +/- 0.04 ml/h). Propranolol, a <beta>-adrenergic-receptor antagonist, blocked the stimulatory effects of ISO; however, it did not affect alveolar fluid reabsorption in control or D A-treated rats. Amiloride (a Na+ channel blocker) and ouabain (a Na+-K+-ATP ase inhibitor), either alone or together, inhibited the stimulatory effects of DA. Colchicine, which disrupts the cellular microtubular transport of i on-transporting proteins to the plasma membrane, inhibited the stimulatory effects of DA, whereas the isomer beta -lumicolchicine did not block the st imulatory effects of DA. These data suggest that DA and ISO increase alveol ar fluid reabsorption in a model of increased Pla by regulating active Natransport in rat alveolar epithelium. The effects of DA and ISO are mediate d by the activation of dopaminergic D-1 receptors and the beta -adrenergic receptors, respectively.