Alveolar macrophages and lung lesions after combined exposure to nickel, cobalt, and trivalent chromium

Abstract

In earlier inhalation exposures of rabbits, nickel increased the production of surfactant by type II cells, with secondary effects on morphology and function of alveolar macrophages. Cobalt induced mainly a nodular growth pattern of the type II cells. Trivalent chromium seemed to impair the capacity of macrophages to catabolize surfactant but did not affect the type II cells. We exposed rabbits by inhalation to combinations of nickel (0.6 mg/m3 as NiCl2) and trivalent chromium [1.2 mg/m3 as Cr(NO3)3] (Ni-Cr), cobalt (0.5 mg/m3 as CoCl2) and nickel (0.5 mg/m3) (Co-Ni), or cobalt (0.5 mg/m3) and chromium (1.2 mg/m3) (Co-Cr) for 4 months, 5 days/week, 6 hr/day. Alveolar macrophages, alveolar type II cells, and lung content of phospholipids were determined. All combined exposures induced more pronounced lung lesions than exposures for each of the metals. Phospholipid concentrations were significantly higher. There were significantly higher percentages of macrophages filled with surfactantlike inclusions and a smooth surface. Accumulations of macrophages in alveoli were more widespread. Chromium potentiated the effects of nickel and cobalt on the type II cells, which led to secondary effects on the macrophages. Nickel potentiated the specific effects of cobalt, i.e., type II cell nodule formation. The result indicates that noxious effects could also be induced in man by combined exposure to nickel, cobalt, and trivalent chromium in concentrations similar to those occurring in some occupational settings.