Morphology and release of lysozyme following exposure of rabbit lung macrophages to nickel or cadmium in vitro.

Lung macrophages lavaged from 7 rabbits were incubated with 0, 3, 6, 12 and 24 micrograms/ml of nickel as NiCl2 and macrophages from 4 rabbits were incubated with 0, 0.1, 1, 3 and 6 micrograms/ml of cadmium as CdCl2. After 2 days lysozyme activity in the medium in which the macrophages were cultivated, was estimated using a technique with agar plates prepared with heat-killed Micrococcus lysodeikticus. Macrophage morphology was examined by scanning and transmission electron microscopy. For nickel there was a dose-related inverse relationship between the lysozyme activity and concentration of nickel. Many macrophages exposed to the higher nickel concentrations had a rounded form and, thus, the surface area of each cell which came in contact with the glass appeared to be less than that for control macrophages. There was, however, no increase in the number of macrophages detached from their glass support. Cadmium exposure did not influence lysozyme levels of activity, in spite of morphological indications of cell toxicity. From the present study we conclude that the decreased lysozyme activity seen previously in vivo after nickel inhalation is likely to be due to a direct effect of nickel ions on macrophages and that the increased lysozyme activity seen in vivo after cadmium inhalation is probably a secondary effect, subsequent to inflammation.