Phagocytosis of particulate nickel compounds by rat peritoneal macrophages in vitro

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Abstract
Phagocytic indices of 17 nickel compounds were measured in vitro in monolayer cultures of rat peritoneal macrophages. The macrophages were exposed for 1 h at 37°C to particles (1.5 μm median diameter) of the nickel compounds, at concentrations of 10 μg/ml of medium (2 μg/cm 2 of monolayer). Phagocytic indices (i.e., the percentages of macrophages with one or more engulfed particles) ranged from 69% (NiO) to 3% (amorphous NiS). In order of decreasing phagocytic indices, the 17 nickel compounds were ranked as follows: NiO > Ni 4 FeS 4 > NiTiO 3 > NiSe > αNi 3 S 2 > Ni > Ni 5 As 2 > NiS 2 > NiFe alloy > NiSb > Ni 11 As 8 > Ni 3 Se 2 > βNiS > NiTe > NiAs > NiAsS > amorphous NiS. Rank-correlation (P 3 S 2 , was a notable exception to the general concordance between phagocytic indices and dissolution half-times: αNi 3 S 2 was avidly phagocytized by macrophages, yet it had one of the shortest dissolution half-times. Preliminary results of carcinogenesis tests of 14 of the nickel compounds do not indicate significant rank-correlation between the phagocytic indices of the nickel compounds and the sarcoma incidences at 1 yr after i.m. administration of the compounds to rats.