Anna Wiernik

Rabbit lung after inhalation of soluble nickel: I. Effects on alveolar macrophages

Alveolar macrophages from eight rabbits, exposed for about 1 month (5 days/week, 6 hr/day) to an aerosol of nickel chloride, 0.3 mg/m3 (as Ni), were studied. The number of macrophages in the lavage fluid and the variance of the cell diameter increased. The macrophages contained laminated structures and most cells had an active cell surface. A few macrophages had a large number of laminated structures and a smooth cell surface. The capacity of the macrophages to reduce nitroblue tetrazolium (NBT) tended to be increased at rest and was significantly increased after stimulation with Escherichia coli. The bactericidal capacity of the macrophages was decreased. The effects were similar to those earlier described after exposure of rabbits for 1 month to about 1 mg/m3 of metallic nickel dust. After exposure both to metallic and soluble nickel the effects are probably caused by an increased amount of surfactant produced by the type II cells in response to nickel ions.

Alveolar macrophage function in nickel dust exposed rabbits

8 rabbits were exposed to metallic nickel dust (2 mg/m3, of which about half was respirable) for 4 weeks. The lungs were lavaged and the macrophages were collected. In comparison with 8 control rabbits, a significant increase was noted in the nickel exposed rabbits as concerned the weight and density of the lungs, the size variation of the lung cells, the phagocytosis of silver coated particles, and the metabolic activity as measured by NBT reduction. The last mentioned increase was recorded during basal conditions as well as during phagocytosis. The NBT reduction during phagocytosis was significantly correlated with the degree of phagocytosis of silver coated particles in both control and exposed rabbits. It is suggested that the exposure to nickel dust has unspecifically activated the macrophages perhaps by increased production of phospholipids.

Rabbit alveolar macrophages after inhalation of soluble cadmium, cobalt, and copper: a comparison with the effects of soluble nickel.

Rabbits were exposed to aerosols of chlorides of cadmium, copper, and cobalt (0.4-0.6 mg/m3 as metal) for 1 month (5 days/weeks and 6 hr/day). The effects of alveolar macrophages were compared with earlier reported effects of nickel chloride (0.3 mg/m3 as Ni). Effects of Cd2+ exposure resembled those of Ni2+ exposure. The number of macrophages in lavage fluid and the variance of cell diameters were thus increased and many cells contained lamellated inclusions. Contrary to macrophages from Ni2+-exposed rabbits, the surface of about 50% of the cells had cytoplasmic blebs. However, such cells were rarely seen by scanning electron microscopy. There were significantly more polymorphonucleated neutrophils and small lymphocytes, suggesting lung parenchymal damage. Cells from Cd2+-exposed animals, like cells from Ni2+-exposed ones, showed an increased oxidative metabolic activity after stimulation with Escherichia coli bacteria. Bactericidal capacity, on the other hand, tended to be enhanced rather than decreased, as in the nickel experiment. After CO2+ exposure, the number of macrophages was slightly increased in the lavage fluid and the cells showed an increased metabolic activity both at rest and upon stimulation with bacteria. Cu2+ exposure gave a slight increase in lamellated inclusions in the macrophages.

Rabbit alveolar macrophages after inhalation of hexa- and trivalent chromium

Rabbits inhaled aerosols of hexavalent chromium (Na2CrO4) and trivalent chromium (Cr(NO3)3) at concentrations of 0.9 and 0.6 mg/m3 of the metal, respectively, for 4-6 weeks (5 days/week and 6 hr/day). Significantly more macrophages were obtained from the lungs of rabbits exposed to Cr(VI) but not from rabbits exposed to Cr(III) as compared with the controls. Macrophages from rabbits exposed to Cr(III) showed several conspicuous changes. About one-third of the macrophages contained round dark inclusions, 0.5-1.5 micron diameter, rich in chromium. Most cells had very large lysosomes which contained membranous fragments of different sizes surrounded by a more homogeneous matrix. Laminated inclusions similar to the lamellar bodies in the type II cells increased in number as did the percentage of cells with a smooth cell surface. Also macrophages from rabbits exposed to Cr(VI) showed morphological changes. The most pronounced one was enlarged lysosomes which contained short lamellae and electron-dense patchy inclusions. Only Cr(III) produced functional changes of the macrophages. The metabolic activity measured by reduction of nitroblue tetrazolium was increased and the phagocytic activity reduced.

Rabbit lungs after long-term exposure to low nickel dust concentration. II. Effects on morphology and function.

For 4 and 8 months (5 days/week, 6 hr/day) rabbits were exposed to 0.13 +/- 0.05 (mean +/- SD) mg/m3 of metallic nickel dust. Volume density of alveolar type II cells was estimated with electron microscopy. Lavaged alveolar macrophages were studied with light and electron microscopy and their abilities to reduce nitroblue tetrazolium (NBT) and to phagocytize particles were tested. The effects seemed to be similar after 4 and 8 months of exposure and when the exposed animals were combined, volume density of type II cells was increased and also significantly correlated with concentration of disaturated phosphatidylcholines in the lung. The macrophages had an active surface. Their NBT activity at rest was increased but a further increase during stimulation with E. coli was low, suggesting an impaired function. Phagocytic activity, however, was not significantly changed.

Rabbit lung after inhalation of manganese chloride: A comparison with the effects of chlorides of nickel, cadmium, cobalt, and copper

Rabbits were exposed to aerosols of MnCl2 (mass median aerodynamic diameter 1 micron) in metal concentrations of 1.1 and 3.9 mg/m3 for 4-6 weeks, 5 days/week, 6 h/day. The effects of alveolar type II cells, phospholipids, alveolar macrophages, and lung structure in general were compared with earlier reported effects of Ni2+, Cd2+, Cu2+, and Co2+. Except for a significant increase in the diameter of the alveolar macrophages after exposure to the higher Mn2+ concentration, no abnormalities were seen. The results of this and earlier studies indicate that these five metal ions have different, specific effects on the alveolar part of the lung.

Rabbit alveolar macrophages after long-term inhalation of soluble cobalt

Rabbits were exposed to 2 or 0.4 mg/m3 of cobalt as CoCl2 for 14-16 weeks (5 days/week and 6 hr/day). More macrophages were lavaged from the lungs of rabbits exposed to the higher Co2+ concentration, and the diameter and variation of the diameter of the macrophages were significantly larger than in controls. The activity of lysozyme in the lavage fluid and in the macrophages was increased in the two exposed groups. Some macrophages in the exposed animals were large and engorged with intracellular lamellar inclusions and lipid droplets. Most of these cells had a smooth surface. The oxidative metabolic activity measured by reduction of nitroblue tetrazolium was increased in the exposed groups. The number of yeast cell particles attached to the surface of the macrophages was increased in the group exposed to the high concentration, but the number of ingested particles was not affected by cobalt exposure. Apart from the fact cobalt increased lysozyme activity whereas nickel decreased it, cobalt produced the same type of effects on macrophages as nickel did in earlier studies. Cobalt affected only a minor proportion whereas nickel affected most macrophages. This can be explained by the fact nickel produced a general increase in the volume density of the type II cells while cobalt affected the type II cells only in some areas of the lungs.

The effect of phospholipid-containing surfactant from nickel exposed rabbits on pulmonary macrophages in vitro.

Alveolar macrophages from 9 normal rabbits were incubated in vitro for 3 h with and without phospholipid-containing surfactant from nickel-treated ones. The macrophages treated with surfactant showed morphological and functional criteria of increased activity. The cell surface had many protrusions and the cytoplasma contained several lamellated structures. The oxidative metabolism, measured by the nitroblue tetrazolium (NBT)-test, at rest and after E. coli stimulation was increased, as was the attachment and ingestion of yeast particles. The NBT-values were about the same as corresponding values of macrophages lavaged from the lungs of nickel-treated rabbit. Macrophages incubated with surfactant from untreated animals, had NBT values and phagocytic activity similar to cells incubated without surfactant. As this substance was administered in excess, the difference in macrophage response would probably be due to a qualitative alteration of the surfactant after nickel exposure.

Alveolar macrophages in rabbits after combined exposure to nickel and trivalent chromium

Rabbits were exposed to a combination of 0.7 mg/m3 Ni2+ as NiCl2 and 1.2 mg/m3 of Cr3+ as Cr(NO3)3, to 0.6 mg/m3 of Ni2+ as NiCl2, or to filtered air for about 4 months, 5 days/week and 6 hr/day. Alveolar macrophages were recovered by lung lavage and studied by light and electron microscopy. Metabolic activity, phagocytic capacity and lysozyme activity in the macrophages were studied. After the combined exposure, the effects on lung weight, number of macrophages, and appearance of surface and number of intracellular laminated inclusions in these cells were more than additive. These effects might be explained by a combination of increased production by Ni2+ and impaired catabolism of surfactant by Cr3+. Because the metal concentrations used were not far above occupational threshold limit values, combined exposures to nickel and trivalent chromium should be considered more seriously.