This study sought to determine if ozone at levels known to induce bronchial hyperreactivity in guinea pigs would inhibit tissue cholinesterase activity. Male, Hartley guinea pigs were exposed to filtered air, 0.1 ppm ozone, or 0.8 ppm ozone for 1 hr. Two hours after exposure, brain, lung, and diaphragm tissue samples were frozen for assay of cholinesterase activity. Brain cholinesterase activity was only minimally inhibited in either ozone exposure group. Both levels of ozone significantly inhibited lung cholinesterase activity compared to control animals' activity: a 17% decrease in activity in the 0.1 ppm ozone group (P less than .05) and a 16% decrease in the 0.8 ppm ozone group (P less than .05). Ozone at 0.8 ppm also inhibited activity in the diaphragm by 14% (P less than .02). To determine the degree of involvement of cholinesterase inhibition in bronchial hyperreactivity, parathion pretreated animals were challenged with histamine and the pulmonary function changes monitored. Parathion-treated animals had a peak resistance increase of 330 +/- 104% (mean +/- SE), while the control vehicle animals' increase was 165 +/- 48%. The differences were not statistically significant, but show that cholinesterase inhibition may contribute to ozone-induced bronchial hyperreactivity.

Animals↗

PubMedDate not supplied

Alteration of pulmonary macrophage intracellular pH following inhalation exposure to sulfuric acid/ozone mixtures.

Recent studies have demonstrated that additive and synergistic effects on rabbit pulmonary macrophages (PM phi) function can occur after combined exposures to acid aerosols and ozone. This study investigated intracellular pH (pHi) homeostasis and H+ extrusion mechanisms of PM phi from rabbits exposed to sulfuric acid, ozone, and their mixtures. Animals were exposed for 3 h to 125 micrograms/m3 sulfuric acid, 0.1, 0.3, 0.6 ppm ozone, or combinations of acid with each concentration of ozone, and the pHi was determined by a fluorescent dye ratioing technique. Exposure to 125 micrograms/m3 acid reduced pHi and exposure to ozone resulted in a concentration-dependent reduction in pHi. Ozone generally tended to mitigate the effect of the acid aerosol on pHi. Other groups of rabbits were exposed to 50 micrograms/m3 sulfuric acid, 0.6 ppm ozone, or their mixture, for 3 h, and PM phi were again harvested. The pHi of PM phi following exposure to each of the pollutant atmospheres was not different from control. However, H+ extrusion with an imposed internal acid load was found to be significantly depressed following exposure to either sulfuric acid or ozone alone, while the mixture produced a significant interaction.

Administration, Inhalation↗