Effect of Phosgene on Rat Lungs after Single High-Level Exposure

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Abstract
Lungs were removed at intervals after rats were exposed under static conditions to phosgene at concentrations within the LCt5Q range and above. Samples were prepared for electron microscopy by standard methodology. This investigation focused on morphologic events taking place in the terminal bronchiolar-alveolar region. The first ultrastructural alteration was vesiculation of cells in the terminal bronchiolar epithelium and most probably represented the beginning of edema in these cells. This was followed by septal extracellular edema with minimal intracellular edema. Intracellular edema developed next and led to cellular disruption and necrosis. As the postexposure period continued, some type II cells developed cellular edema, and on a focal basis type I cells were disrupted. Fluid appeared in the alveoli after the intracellular and extracellular interstitial spaces of the septa became very swollen. In spite of this widespread interstitial edema, large areas of the cells comprising major portions of the air-blood barrier were tenaciously adherent to areas of the fused basement membrane. Interstitial cells seem to be very susceptible to the effects of edema, but it is not possible on the bVsis of this study to determine whether these cells are specific targets of phosgene chemical reaction. Metabolic depression and disturbance, as judged by decreases in enzymatic activity, may precede major ultrastructural changes in the alveolar region.