Morphometry of In Situ and Lavaged Pulmonary Alveolar Macrophages from Control and Ozone-Exposed Rats

Abstract

Effects of ambient levels of ozone on cell size and compartments were determined morphometrically for both in situ and lavaged pulmonary alveolar macrophages from rats exposed to filtered air or to filtered air with 0.60 ppm ozone. The ozone exposure was 8 hr/day for 3 days. Significant exposure-related compartmental volume density changes of in situ centriacinar macrophages were: decreased endoplasm (p < 0.01); increased lysosome-like structures (p < 0.01); decreased primary lysosomes (p < 0.01); increased small and large secondary lysosomes (p < 0.001); and decreased phagosomeslautophagosomes (p < 0.05). In lavaged macrophages, the only significant exposurerelated change was an increase in the density of large secondary lysosomes (p < 0.01). Mean profile areas of in situ centriacinar macrophages from control and exposed rats were 86.94 μm² and 112.04 μm², respectively. The average mean cell volume V and mean caliper diameter D of macrophages lavaged from control rats were 1128.45 μ³ and 12.92 μm, respectively, whereas those from exposed rats were 1583–08 μm³ and 14.46 μm, respectively. Exposure-related increases in cell size were seen in both in situ and lavaged macrophages, but more significant differences in cell compartments were seen in the in situ centriacinar macrophages. Morphometry of pulmonary alveolar macrophages after ambient levels of ozone indicated increased uptake, storage, or both rather than cell damage. Comparison of in situ centriacinar and lavaged macrophages from both control and exposed rats revealed significant differences in their volume fractions of nucleus, cytoplasm, ectoplasm, mitochondria, lysosome-like structures, lipid droplets, vacuoles, and phagosome/autophagosomes. These differences between centriacinar and lavaged macrophages indicate different cell populations are sampled by these two methods.