SPECIES-DIFFERENCES IN IMPAIRMENT AND RECOVERY OF ALVEOLAR MACROPHAGE FUNCTIONS FOLLOWING SINGLE AND REPEATED OZONE EXPOSURES

Effects of single (0.4 ppm for 3, 6, or 12 hr) and repeated (0.4 ppm, 12 hr/day for 3 or 7 days) in vivo ozone exposures on rat and mouse alveolar macrophage functions and cell number were investigated. Single ozone exposure of rats resulted in a small (∼15%) decrease in Fc-receptor-mediated phagocytosis and phorbol ester-induced superoxide production by the alveolar macrophages and was followed by recovery above control levels within 12 hr of exposure. Repeated exposures of rats for up to 7 days did not alter alveolar macrophage functions, with the exception of the effects of 3 days of exposure on superoxide production (71 ± 9% as compared with the controls). In mice, significant changes in alveolar macrophage functions were not observed until 12 hr of exposure (at that timepoint phagocytosis was 74 ± 2%). Repeated ozone exposures of mice did not cause a further decrease in phagocytosis (at Day 7, 74 ± 14%). Both after 3 and 7 days of repeated ozone exposure of mice, superoxide production by the alveolar macrophages was inhibited ∼50%. In rats and mice, repeated ozone exposures led to an increase in the number of alveolar macrophages. In mice, this increase appeared at a later time point (at Day 7 vs Day 3) and was less pronounced (at Day 7, 139 ± 9% vs 179 ± 17%) as compared with rats. In summary, our data show that rat and mouse alveolar macrophages have different susceptibilities to both single and repeated in vivo ozone exposures. © 1991.