Inhalation toxicity of soman vapor in non-anesthetized rats: A preliminary assessment of inhaled bronchodilator or steroid therapy

• We developed a rodent inhalation exposure model for chemical warfare nerve agents.
• Determined the LCt50 of soman in untreated, non-anesthetized rats.
• Observed acute respiratory toxicity and lung injury following soman exposure.
• Evaluated the efficacy of inhaled Combivent or Symbicort.
• Treatments resulted in improvements in minute volume and edema, but not lethality.

Respiratory toxicity, injury and treatment following vapor inhalational exposure to the chemical warfare nerve agent (CWNA) soman (GD) were examined in non-anesthetized rats. This study exposed male Sprague–Dawley rats (250–300 g) to 520, 560, 600, 825 or 1410 mg × min/m3 of soman in a customized head-out inhalation system. Signs of CWNA-induced cholinergic crises were observed in all soman-exposed animals. The LCt50 of vaporized soman as determined by probit analysis was 593.1 mg × min/m3. All animals exposed to 825 and 1410 mg × min/m3 developed severe convulsions and died within 4–8 min post-exposure. Edema measured by wet/dry weight ratio of the left lung lobe increased in a dose-dependent manner in all soman-exposed animals. Bronchoalveolar lavage (BAL) fluid and blood acetylcholinesterase (AChE) activities were inhibited dose-dependently in soman-exposed groups at 24 h. A significant increase in total BAL protein was observed in soman-exposed animals at all doses. AChE activity was inhibited in lung and whole brain tissues in all soman-exposed animals. Histopathological analysis of the lungs of animals exposed to 600 mg × min/m3 of soman revealed prominent morphological changes including alveolar histiocytosis, hemorrhage and inflammation consisting of neutrophilic exudate. Exposure of animals to 600 mg × min/m3 of soman followed by treatment with two actuations for 10 s of Combivent (21 μg of ipratropium bromide and 120 μg of albuterol sulfate) and Symbicort (80 μg budesonide and 4.5 μg formoterol) by inhalation into a modified metered dose inhaler (MDI) 10 min post-exposure resulted in increased minute volume, but did not decrease mortality. These results indicate that inhalation exposure to soman vapor causes acute respiratory toxicity and injury in untreated, un-anesthetized rats and that inhalation treatment with Combivent or Symbicort did improve the respiratory outcomes, but did not influence lethality.