Dopamine increases active na+ transport and lung liquid clearance

In order for pulmonary edema to be cleared, sodium (and subsequently water) must be transported out of the alveolar space. This active transport is mediated in part by the Na,KATPase located on the basolateral alveolar epithelial membrane. We investigated the role of dopamine in regulating active Na+ transport and thus the ability of the pulmonary alveolar epithelium to dear alveolar fluid. Studies carried out in isolated perfused rat lungs showed that 10 M dopamine instilled into the alveolar space increased clearance by approximately 30% above controls, from 0.56 ±0.04 ml/hr (n-10) to 0.75 ±0.09 ml/nr (n-4). Coinstillation of 10" M propranolol with the dopamine to block possible p-adrenergic effects of dopamine did not affect the increased clearance mediated by dopamine, as clearance increased to 0.75 ±0.11 (n-5). We conclude that dopamine is capable of mediating enhanced liquid clearance by the alveolar epithelium, and that this is not mediated by activation of βadrenergic receptors. We hypothesize that this augmentation is possibly mediated by either increased Na+ channels or increased Kla.K-ATPase activity located on the alveolar epithelial cells, or both.