Sulfuric acid-induced airway hyperresponsiveness.

Rabbits were exposed to submicrometer sulfuric acid (H2SO4) mist at 250 micrograms/m3 for 1 hr/day, 5 days/week for 4, 8, or 12 months in order to examine the effects on bronchial responsiveness, which was assessed at the end of each exposure series by administration (iv) of doubling doses of acetylcholine and measurement of pulmonary resistance (RL). Dynamic compliance (Cdyn) and respiratory rate (f) were also measured following agonist challenge. Animals exposed for 4 months showed increased sensitivity to acetylcholine (dose required to produce a 150% increase in RL), and there was an increase in reactivity (slope of dose vs change in RL) by 8 months, with a leveling off of the response after this time. No changes in Cdyn or f were noted at any time. Thus, repeated exposures to H2SO4 resulted in the production of hyperresponsive airways in previously healthy animals. This has implications for the role of nonspecific irritants in the pathogenesis of airway disease.