Isolation of pulmonary alveolar type I cells from adult rats

The authors have developed a procedure for the isolation of alveolar Type I (ATI) cells from adult rat lung. After an initial selective enzymatic digestion of the lungs by lavage with 0.2% collagenase, 0.05% trypsin, 0.008% elastase, and 0.005% DNAse Type I, the cells which are released are separated by density gradient centrifugation, and a fraction which includes all ATI cells (density, 1.0177-1.0411) is harvested. Contaminating leukocytes are excluded by specific surface adsorption, exploiting the fact that these cells have leukocyte common antigen on their surfaces, whereas ATI cells do not. Similarly, contaminating alveolar Type II (ATII) cells are removed by specific surface adsorption with the use of the lectin Maclura pomifera agglutinin, which binds to freshly isolated ATII cells and not to ATI cells. Our procedure yields 5 X 10(6) ATI cells per rat in a fraction that is at least 85-88% pure; the cells are immediately available for biochemical or pharmacologic analysis and represent a 98% recovery of the ATI cells loaded onto the density gradient. The ATI cells retain their essential in vivo morphologic characteristics, including their polarity.