Quantitation of Damage to the Alveolar Epithelium by Means of Type 2 Cell Proliferation1

Abstract

The purpose of this study was to determine whether the amount of alveolar epithelial tissue damaged during exposure to NO₂ could be quantified by measuring the proliferative response to Type 2 cells. To accomplish this, we used tissues from previously published experiments in which rats had been exposed to NO₂ and the proliferative response of Type 2 cells had been measured during a 5-day period. The proportion of alveolar epithelium damaged was determined by stereologic examination with electron microscopy of tissue sections from those rats exposed to NO₂ for 24 hours. These values were then compared with the total proliferative response of Type 2 cells for the 5 days of exposure. The study demonstrated that increasing tissue damage is associated with a greater proliferative response of Type 2 cells. The high degree of correlation (r = 0.93) indicates that the proliferative response of Type 2 cells can be used as an indirect means to quantify acute damage to the alveolar epithelium.