An improved method for calculating labeling indices of lung epithelial and interstitial cells.

The sampling method was developed as an improvement in calculating labeling indices (LIs) of epithelial and interstitial cells in the airways and alveolar region of the lungs of rats. This method is more accurate and requires less time than the traditional cytokinetic methods, which involve counting all labeled and unlabeled cells. In the sampling method, all labeled cells are counted, but the total number of cells is estimated based on a representative sample count of airway and alveolar cells in each animal. The LIs as calculated by the two methods correlated very well (r greater than 0.97). The small amount of error introduced by estimating the total number of cells was more than compensated for by the increased accuracy associated with a larger sample size.