Low level chromium (VI) inhalation effects on alveolar macrophages and immune functions in Wistar rats

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Abstract
In inhalation chambers, 5-week-old male Wistar rats of the strain TNO-W-74 were continuously exposed to submicron aerosols of sodium dichromate in concentrations from 25 (low level) to 200 μg/m3 Cr (high level). Subacute exposure (28 days) to 25 and 50 μg/m3 Cr resulted in “activated” alveolar macrophages with stimulated phagocytic activities, and significantly elevated antibody responses to injected SRBC's. After subchronic (90 days) low level exposure there was a more pronounced effect on activation of the alveolar macrophages, with increased phagocytic activities. However, at high Cr (VI) exposure level (200 μg/m3), inhibited phagocytic function of the alveolar macrophages was seen. In rats which were exposed to this chromium aerosol concentration for 42 days, the lung clearance of inert iron oxide was reduced significantly. The humoral immune system was still stimulated at subchronic low chromium aerosol concentrations of 100 μg/m3, but significantly depressed at 200 μg/m3 Cr. These results show that respiratory defence and immunologic functions were stimulated or inhibited depending on dose and time of chromium (VI) inhalation.