Alteration of Pulmonary Macrophage Intracellular PH Following Inhalation Exposure to Sulfuric Acid/Ozone Mixtures

Abstract

Recent studies have demonstrated that additive and synergistic effects on rabbit pulmonary macrophages (PMø) function can occur after combined exposures to acid aerosols and ozone. This study investigated intracellular pH (pH_i) homeostasis and H⁺ extrusion mechanìsms of PMø from rabbits exposed to sulfuric acid, ozone, and their mixtures. Animals were exposed for 3 h to 125 μg/m³ sulfuric acid, 0.1, 0.3, 0.6 ppm ozone, or combinations of acid with each concentration of ozone, and the pH_i was determined by a fluorescent dye ratioing technique. Exposure to 125 μg/m³ acid reduced pH_i and exposure to ozone resulted in a concentration-dependent reduction in pH_i. Ozone generally tended to mitigate the effect of the acid aerosol on pH_i. Other groups of rabbits were exposed to 50 μg/m³ sulfuric acid, 0.6 ppm ozone, or their mixture, for 3 h, and PMø were again harvested. The pH_i of PMø 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.

Key Words:

• intracellular pH
• macrophage
• ozone
• acid aerosol
• rabbit