Effects of Nitrogen Dioxide on Alveolar Epithelial Barrier Properties

This report describes a study by Dr. Crandall and colleagues to investigate the ability of nitrogen dioxide (NO₂) to adversely alter the barrier and transport properties of mammalian alveolar epithelium and cause pulmonary edema. Rat type II alveolar cell monolayers cultured on non-porous and porous surfaces were used as models of isolated alveolar epithelium for in vitro exposure to NO₂. Changes in the volume of fluid-filled domes thought to result from active solute transport from medium to substratum and subsequent passive water transport were used as a transcellular transport markers. The difference in the number and volume of domes presenting pre- versus post- NO₂ exposure was quantified to determine the effect of NO₂ on transport. Another set of experiments exposed the cells to NO₂ and measured bioelectric tissue resistance, using decrements in tissue resistance as an indicator of increased paracellular permeability.