Counting parenchymal cells in the goat lung with serial section reconstruction and stereology

Information about numbers of cells is needed to interpret cellular and tissue responses to injury. As a first step towards identifying changes in cell number and structure in injured lungs, this study reports the frequencies of 4 parenchymal cell types in the normal goat lung. Cells were counted using serial section reconstruction and light microscopy. Relative cell frequencies were (mean +/- standard error): type I cells (5.47 +/- 0.52%), type II cells 10.74 +/- 1.17%), capillary endothelial cells (47.50 +/- 1.42%), and interstitial cells (37.14 +/- 3.00%). These cell counts coming from serial section reconstructions allowed us to estimate mean nuclear diameters of the 4 cell types without assumptions for size, shape, and frequency distribution, and they were also used to evaluate counts of nuclear profiles taken from light and electron micrographs. When the same mean nuclear diameter was used, the counts of nuclear profiles from both light and electron microscopy gave similar stereological estimates for cell numbers, provided section compression was corrected. We conclude that lung parenchymal cells can be counted using light microscopy and serial section reconstruction and that this information provides a standard for evaluating stereological estimates of cell numbers.