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Phagocytosis of particulate nickel compounds by rat peritoneal macrophages in vitro
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 degrees C to particles (1.5 micrometer median diameter) of the nickel compounds, at concentrations of 10 microgram/ml of medium (2 microgram/cm2 of monolayer). Phagocytic induces (i.e., the percentages of macrophages with one or more engulfed particles) ranged from 69% (NiO) to 3% (amorphous NiS). In order to decreasing phagocytic indices, the 17 nickel compounds were ranked as follows: NiO greater than Ni4FeS4 greater than NiTiO3 greater than NiSe greater than alpha Ni3S2 greater than Ni greater than Ni5As2 greater than NiS2 greater than NiFe alloy greater than NiSb greater than Ni11As8 greater Ni3-Se2 greater than beta NiS greater than NiTe greater than NiAs greater than NiAsS greater than amorphous NiS. Rank-correlation (P less than 0.03) was observed between the phagocytic indices of the nickel compounds and their dissolution half-times in rat serum. Nickel subsulfide, alpha Ni3S2, was a notable exception to the general concordance between phagocytic indices and dissolution half-times: alpha Ni3S2 was avidly phagocytized by macrophages, yet it had one or 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.
Insights
Phagocytic activity of nickel compounds by rat macrophages varied greatly, with nickel oxide (NiO) showing the highest index and amorphous nickel sulfide (NiS) the lowest. Phagocytosis correlated with dissolution rates, except for nickel subsulfide (α Ni3S2).
Area of Science:
- Toxicology
- Cell Biology
- Materials Science
Background:
- Macrophages play a crucial role in the innate immune system, engulfing foreign particles.
- Nickel compounds are widely used industrially, necessitating an understanding of their biological interactions.
- The phagocytic uptake of nickel compounds by macrophages is a key factor in their toxicological profile.
Purpose of the Study:
- To evaluate and rank the in vitro phagocytic indices of 17 different nickel compounds using rat peritoneal macrophages.
- To investigate the correlation between the phagocytic activity of nickel compounds and their dissolution rates in rat serum.
- To explore potential correlations between phagocytic indices and carcinogenicity data.
Main Methods:
- In vitro exposure of rat peritoneal macrophages to 17 nickel compounds at a concentration of 10 μg/ml for 1 hour at 37°C.
- Measurement of phagocytic indices, defined as the percentage of macrophages engulfing particles (1.5 μm median diameter).
- Comparison of phagocytic indices with dissolution half-times in rat serum and preliminary carcinogenicity data.
Main Results:
- Phagocytic indices ranged from 69% for NiO to 3% for amorphous NiS, with a clear ranking of compounds observed.
- A significant rank-correlation (P < 0.03) was found between phagocytic indices and dissolution half-times in rat serum.
- Nickel subsulfide (α Ni3S2) was highly phagocytized despite having a short dissolution half-time, indicating a complex interaction.
Conclusions:
- The phagocytic uptake of nickel compounds by macrophages is highly variable and depends on the specific compound.
- Dissolution rate is a significant, but not the sole, determinant of nickel compound phagocytosis.
- Further research is needed to fully elucidate the relationship between nickel compound phagocytosis, dissolution, and long-term toxicity, including carcinogenicity.