[Transport of ions across alveolar epithelial cells in resected human lungs]

Little information is available regarding the effect of ion transport agonists and antagonists on ion transport in the human lung. Therefore, we studied ion transport in lungs resected from patients with lung cancer. A test solution of 45 ml of isosmotic albumin was instilled into one segment of a resected lobe within 10 min of resection. Because protein leaves the air space very slowly, the concentration of alveolar protein over 4 h was used to quantify the volume of alveolar fluid. Ion transport was measured from the changes in ion concentrations and the volume of alveolar fluid. In the basal condition, the net efflux of Na+ and Cl- were 4.66 +/- 0.83 mEq/l/h and 3.52 +/- 0.84 mEq/l/h, respectively. In contrast, the net influx of K+ was 0.44 +/- 0.07 mEq/l/h. Amiloride (10(-5) M), an inhibitor of apical Na+ uptake, ouabain (10(-3) M), an inhibitor of Na(+)-K+ ATPase, and hypothermia (8 degrees C) reduced the efflux of Na+ and Cl-. Ouabain and hypothermia increased the net influx of K+. Terbutaline (10(-3) or 10(-4) M) increased the efflux of Na+ and Cl-, but did not affect the influx of K+. Propranolol (10(-4) M) and amiloride (10(-5) M) inhibited the terbutaline-induced increase in the transport of Na+ and Cl-. Alveolar fluid clearance was closely correlated with Na+ transport and with Cl- transport. However, the values of Na+ transport were greater than those of Cl- transport. These data suggest that Na+ transport is accompanied by Cl- transport and fluid movement out of the alveolar space in resected human lungs.