Journal of Applied Physiology, Vol 50, Issue 4 754-760, Copyright © 1981 by American Physiological Society
Bronchial reactivity to inhaled methacholine in cigarette-smoking baboons
J. D. Roehrs, W. R. Rogers and W. G. Johanson Jr
We expected that cigarette smoking would increase airway reactivity to
inhaled methacholine. To remove the self-selection bias inherent among
humans, we randomly assigned young male baboons (Papio cynocephalus) to
cigarette-smoking or sham-smoking groups. The animals were taught to puff
on lit cigarettes (smokers) or on a similar resistance (shams). After 6
pack-yr of smoking (40 cigarettes/day for 3 yr), we studied airway
reactivity. The animals were anesthetized and intubated for measurement of
lung volumes, compliance, and expiratory flow with air and with 80%
helium-20% oxygen using both partial expiratory flow-volume and maximal
expiratory flow-volume maneuvers. Baseline lung function was similar in
smokers and shams. Following methacholine, residual volume increased
significantly (P less than 0.05) in shams but not in smokers. Smokers
showed significantly (P less than 0.04) greater postchallenge flow rates
than did shams, and the dose of methacholine required to produce a 20%
decrement in flow was significantly (P less than 0.05) greater in smokers.
Chronic cigarette smoking in a nonhuman primate model decreases airway
reactivity to inhaled methacholine even when base-line lung function is
normal.
