METHACHOLINE-INDUCED PULMONARY GAS TRAPPING IN GUINEA-PIGS, HAMSTERS,MICE, AND RATS

Postmortem pulmonary gas trapping was investigated as an index of in v ivo airway obstruction following methacholine inhalation in four diffe rent rodent species. Male guinea pigs (Hartley), hamsters (golden Syri an), mice (A/J, BALB/c, and ICR), and rats (Brown-Norway, Fischer 344, Lewis, and Sprague-Dawley) were exposed to aerosols of methacholine o r sodium chloride. Maximum excised lung gas volumes (ELGV) of methacho line-exposed guinea pigs, hamsters, mice, and rats were 2.3-8.7 times those of sodium chloride-treated animals. Mean ELGV values of sodium c hloride-exposed animals ranged from 1.50 +/- 0.20 ml/kg for guinea pig s to 2.75 +/- 0.20 ml/kg for Brown-Norway rats. Although all species r esponded to methacholine, guinea pigs were the most responsive, with s imilar to 1.6 mu g/kg of inhaled methacholine needed to increase ELGV to 200% of control. Compared with guinea pigs, hamsters, mice, and rat s were 11- to 1,395-fold less responsive. Although hamsters, mice, and rats are less sensitive than guinea pigs to the airway-obstructive ef fects of methacholine, pulmonary gas trapping appears useful as a meas ure of airway responses in these species.