Indomethacin increases bronchial reactivity after exposure to subthreshold ozone levels.

We investigated the effects of indomethacin on bronchial reactivity after ozone exposure. Guinea pigs in groups of six were treated with indomethacin (30 mg/kg IP) and studied before and 2 h after a 2 h exposure to either 1.5 or 3.0 ppm ozone. These animals were compared to similarly exposed groups that were untreated. Reactivity was determined by measuring specific airway resistance (SRaw) upon intravenous acetylcholine infusion. Prior to ozone exposure, indomethacin had no effect on either SRaw or muscarinic reactivity. In all untreated guinea pigs (n = 12) exposed to 1.5 ppm ozone, there was no significant change in SRaw or muscarinic reactivity. In contrast, all treated animals exposed to 1.5 ppm showed a substantial increase in reactivity. Those treated animals exposed to 3.0 ppm showed significant elevations in SRaw, making interpretations of changes in their reactivity difficult. We conclude that indomethacin treatment increases bronchial reactivity in guinea pigs exposed to subthreshold ozone levels.