Density-independent isolation of type II pneumocytes after partial pneumonectomy

Type II pneumocytes were isolated by immunoglobin G (IgG) panning from the lungs of normal rats and the right lung of rats (180-200 g) subjected to left pneumonectomy. Cells were studied at 7 (pnx-7) and 15 (pnx-15) days postoperative, times during and after, respectively, rapid compensatory growth of the right lung. After 24 h of primary culture, pnx-7 cells contained 32% more protein per DNA, and incorporated thymidine at a rate 224% greater than cells isolated from control rats. Both the protein-to-DNA ratio and thymidine incorporation returned to control values in pnx-15 cells. Uptake of exogenous spermidine also was increased by 50% in pnx-7 cells at 24 h of primary culture and returned to control values in pnx-15 cells. Increased spermidine uptake was due to an increase in the maximal velocity (Vmax) of transport from 30.3 (control) to 45.5 pmol.micrograms DNA-1.h-1 (pnx-7), with no change in the apparent Km of 1.32 microM. No change was observed in the relative rates of phospholipid or neutral lipid biosynthesis. The increases in thymidine incorporation and spermidine uptake were significantly greater than those previously observed [Am. J. Physiol. 254 (Cell Physiol. 23): C684-C690, 1988] in pnx-7 cells isolated by Percoll gradient sedimentation. These results suggest that pnx-7 lungs contain distinct subpopulations of type II pneumocytes, the recovery of which is dependent on the cell isolation protocol employed.