Chronic cigarette smoke inhalation and aging in mice: 2. Quantitation of the pulmonary macrophage response

Effects of chronic cigarette smoke inhalation on population size, cell dimensions and ultrastructure of in situ pulmonary macrophages of young and old C57BL/6 mice have been assessed. Smoke exposure occurred over a 9-month period beginning when young animals were 2 months of age and old mice 8 to 10 months. Quantitative data revealed that chronic smoke exposure significantly elevates the pulmonary macrophage population size over control values. However, the number of phagocytes was more than three times greater in young smoke-exposed mice when compared to that of the old. Mean area and diameter of pulmonary macrophages in young and old smoke-exposed animals were significantly larger than those of controls. Morphometric data indicate that pulmonary macrophage enlargement in old smoke-exposed animals was due to increased numbers and size of secondary lysosomes and accumulation of inclusions resembling crystalline kaolinite within the cells. More than one percent of cell volume was occupied by this material. Evaluation of dimensional changes of organelles involved in synthesis and metabolism suggests that smoke inhalation had no measurable effect on or slightly depressed these activities. Data reported indicate that the lysosomal system is altered differentially in smoke-exposed young and old animals.