Effects of Diesel engine exhaust on pulmonary alveolar macrophages

The in vivo effects of inhalation of diesel engine exhaust (DEE) on pulmonary alveolar macrophages (PAM) was studied in 73 guinea pigs and 48 rats. Animals were exposed in individual cages in special chambers to 3 different dose levels of DEE expressed in terms of the concentation of soot or carbon particles (-P); 250, 1500, 6000 micrograms DEE-P/M3. Exposure durations for guinea pigs were 1 and 3 days, 1 and 2 weeks, 2, 4, 8 and 12 months while rats were exposed 1, 2, 4, 8 and 12 months. Age matched controls were similarly exposed concurrently to "clean" air. PAM obtained by bronchopulmonary lavage from exposed animals had viabilities comparable to controls. PAM diameters and relative surface areas increased 2--3 fold over controls and in relation to both the dose of DEE-P given and the exposure duration. Most of the in vivo exposed PAM had phagocytized DEE-P which did not appear to be cytotoxic and remained confined in phagosomes as discrete particles with diameters of 0.014--0.072 micrometer. Ability of PAM to adhere and spread on test surfaces was greater in the DEE-P sets than in controls. DEE-P containing PAM were still able to phagocytize latex particles when fed in vitro. However, such PAM had defective phagocytosis ability, and did not in the same time interval take up as much fluorescent latex as controls when studied by flow system technology. Absolute numbers of PAM in guinea pig lavages from exposures to 250 and 1500 microgram DEE-P/M3 for 2 months were not significantly changed over concurrent controls. Exudative leukocytes (eosinophils in guinea pigs and neutrophils in rats) appeared in the lavage in greater numbers as dose and duration of exposure increased. Another species difference was the appearance in DEE-P exposed guinea pig lavages of "reactive" monocytes.