Effects of ozone on peripheral lung reactivity

In previous studies, we demonstrated that local exposures to the lung periphery to 0.1 ppm ozone (O3) produce increases in resistance to flow through the collateral system (Rcs) which are prevented by vagotomy, and the local exposures to 1.0 ppm O3 produces increases in Rcs which are only partially mediated by the parasympathetic system. In the present studies, we evaluated the effects of short exposures to O3 on reactions to H2O and histamine in anesthetized male dogs when no residual effects of the O3 exposures could be detected. For this purpose a fiber-optic bronchoscope was wedged in a segmental airway of anesthetized dogs and was used to deliver O3, aerosols of H2O, histamine (1.5 X 10(-4) mg), and atropine (0.1 mg). Measurements of Rcs were used to monitor responses to these agents. Responses to three successive challenges with H2O and with histamine were not different from each other. A 30-min exposure to 0.1 ppm O3 between the first and second challenge did not alter responses to histamine or H2O. However, a 10-min exposure to 1.0 ppm O3 resulted in a significant increase in responses to both H2O and histamine. No correlation was noted between the magnitude of response to O3 and the increase in response to histamine or H2O following O3 exposure. Parasympathetic blockade (atropine or bilateral cervical vagotomy) abolished the increase in response to H2O but not the increase in response to histamine following exposure to 1.0 ppm O3.(ABSTRACT TRUNCATED AT 250 WORDS)