Effects of ammonium sulfate aerosol exposure on lung structure of normal and elastase-impaired rats and guinea pigs.

Rats and guinea pigs, pretreated with intratracheally administered elastase or saline, were exposed to 1.03 mg/m3 (NH4)2SO4; MMAD, 0.42 micron. Identically treated controls were sham exposed. Measurements and evaluation of structural changes were conducted using morphometric techniques on SEM photographs and by applying subjective ratings. Pathology studies were conducted by light and electron microscopy. All examination methods confirmed elastase-induced emphysema, which was aggravated by (NH4)2SO4 exposure in the rat. Ammonium sulfate exposure of saline-treated animals produced measurable degrees of enlargement of alveoli, and alveolar ducts and sacs. Electron microscopy revealed increased interstitial collagen in affected lung areas of elastase-treated, (NH4)2SO4-exposed animals. Alveolar-pore size was significantly increased in elastase-treated animals (control and exposed) but not in saline-treated, exposed animals. The data suggest a possible difference between elastase and (NH4)2SO4 in the mechanisms responsible for the increased diameter of alveolar structures. Hypertrophy and hyperplasia of nonciliated epithelial cells of the small airways and of the Type II alveolar cells were observed in otherwise untreated guinea pigs exposed to (NH4)2SO4 but not in elastase-treated guinea pigs, nor in any of the rats.