Hyperosmotic-induced bronchoconstriction in the canine lung periphery

Abstract

Hypertonic aerosol- and dry airflow-induced bronchoconstriction were examined in the canine lung periphery by the use of a wedged bronchoscope technique. Collateral resistance was measured in anesthetized dogs before and after exposure to isotonic and hypertonic aerosols and dry airflow. Hypertonic aerosols produced significantly greater responses than isotonic aerosols, and resistance increased in an exposure-dependent manner. Atropine attenuated responses to these challenges, indicating that aerosol-induced peripheral lung constriction was, in part, muscarinic in origin. Paired hypertonic- and dry airflow-induced constriction exhibited marked differences in magnitude and time course: responses to hypertonic aerosol peaked immediately; dry air-induced responses rose slowly to a maximum 5-min postchallenge. These differences may reflect differences in stimulus strength or differences in the regulatory pathways activated by each challenge. Despite this, a significant correlation exists between aerosol- and dry air-induced responses in the canine lung periphery and suggests that changes in airway fluid osmolality have an important role in the initiation of airflow-induced bronchoconstriction.