Acute Lung Injury Following Inhalation Exposure to Nerve Agent VX in Guinea Pigs

A microinstillation technique of inhalation exposure was utilized to assess lung injury following chemical warfare nerve agent VX [methylphosphonothioic acid S-(2-[bis(1-methylethyl)amino]ethyl) O-ethyl ester] exposure in guinea pigs. Animals were anesthetized using Telazol-meditomidine, gently intubated, and VX was aerosolized using a microcatheter placed 2 cm above the bifurcation of the trachea. Different doses (50.4 μg/m³, 70.4 μ g/m^m3, 90.4 μg/m^m3) of VX were administered at 40 pulses/min for 5 min. Dosing of VX was calculated by the volume of aerosol produced per 200 pulses and diluting the agent accordingly. Although the survival rate of animals exposed to different doses of VX was similar to the controls, nearly a 20% weight reduction was observed in exposed animals. After 24 h of recovery, the animals were euthanized and bronchoalveolar lavage (BAL) was performed with oxygen free saline. BAL was centrifuged and separated into BAL fluid (BALF) and BAL cells (BALC) and analyzed for indication of lung injury. The edema by dry/wet weight ratio of the accessory lobe increased 11% in VX-treated animals. BAL cell number was increased in VX-treated animals compared to controls, independent of dosage. Trypan blue viability assay indicated an increase in BAL cell death in 70.4 μg/m^m3 and 90.4 μg/m^m3 VX-exposed animals. Differential cell counting of BALC indicated a decrease in macrophage/monocytes in VX-exposed animals. The total amount of BAL protein increased gradually with the exposed dose of VX and was highest in animals exposed to 90.4 μg/m^m3, indicating that this dose of VX caused lung injury that persisted at 24 h. In addition, histopathology results also suggest that inhalation exposure to VX induces acute lung injury.