Response of pulmonary cellular defenses to the inhalation of high concentrations of diesel exhaust

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Abstract
Rats were exposed to 3 concentrations of diluted diesel exhaust for 6 mo. and 1 yr. Bronchopulmonary lavage was used to obtain the pulmonary phagocytes from the animals to study the response of the phagocytic defenses to the inhaled particulate. The cell numbers and volumes were measured using an electronic particle counter. The cell counts of alveolar macrophages (AM) were proportional to the concentration of diesel exhaust particulate (DP) in the chronic exposures. AM increased in the lungs in response to the rate of DP mass entering the lungs, rather than to the total DP burden in the lung. The geometric mean volumes of AM from the exposed and control animals were .apprx. 1100 .mu.m3 at 6 and 12 mo. of exposure, although exposed cell-volume distributions skewed towards larger sizes. The AM volume distributions extended to 2000 .mu.m3 in control and 250 .mu.g DP/m3 exposed animals and up to 5000 .mu.m3 in cells from animals exposed to 750 and 1500 .mu.g DP/m3. The volume distributions were reproducible in equivalent control and exposed cell populations. Polymorphonuclear leukocytes were present in the lavaged cell populations from the animals exposed to 750 and 1500 .mu.g/m3. At 1 yr of exposure, lymphocytes were also lavaged from animals exposed to 750 and 1500 .mu.g DP/m3. Protein, .beta.-glucuronidase activity and acid phosphatase activity were measured in the lavaged cells, and were elevated in the cells from animals exposed to 750 and 1500 .mu.g/m3. The buoyant density of diesel-laden AM was greater than that of control AM, and overlapped with the buoyant density of the polymorphonuclear leukocytes.

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