Alveolar Epithelial Fluid Transport Can Be Upregulated Simultaneously in Rats by Two Different Mechanisms

Materials and Methods

Rats were instilled by the intratracheal route with either KGF (5 mg/kg) or saline solution (control rats). Several studies were carried out subsequently at 48, 72, 120, and 240 h. First, the in vivo effect of KGF on alveolar epithelial type II cell mitogenesis was determined by using bromodeoxyuridine (BrdU) and a specific alveolar epithelial type II cell monoclonal antibody (courtesy, L. Dobbs). Alveolar fluid clearance was studied in rats previously instilled with KGF or saline solution

Results

Alveolar fluid clearance was increased significantly compared with control studies at 48, 72, and 120 h (Table 1). The peak of alveolar liquid clearance was at 72 h. By 240 h, alveolar fluid clearance had returned to baseline levels. There was an excellent correlation between the increase in alveolar fluid clearance in the KGF-treated rats and the increase in the number of alveolar epithelial type II cells (r = 0.92, p < 0.02).

Furthermore, terbutaline increased alveolar epithelial fluid

Discussion

The results of these studies demonstrate that one dose of KGF induced a sustained increase in the capacity of the alveolar epithelium to transport fluid from the airspaces of the lung for 120 h. Since there was a good correlation between the number of alveolar epithelial type II cells and the rate of alveolar liquid clearance, the primary mechanism for the KGF effect is explained by the increase in the number of alveolar type II cells. Thus, this study establishes that an important mechanism