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Phagocytosis of Nickel Subsulfide Particles during the Early Stages of Neoplastic Transformation in Tissue Culture¹

Division of Toxicology, Department of Pharmacology, University of Texas Medical School at Houston, Houston, Texas 77025 [M. C.], and Veterinary Toxicology and Entomology, Research Laboratory AR/SEA, United States Department of Agriculture, College Station, Texas 77843 [H. H. M.]

Cellular uptake of crystalline Ni₃S₂ particles (a potent carcinogen) and amorphous NiS particles (a noncarcinogen) were studied using light and electron microscopy. Cultured Syrian hamster embryo cells and Chinese hamster ovary cells actively phagocytized Ni₃S₂ particles (5 µm) but did not take up NiS particles (5 µm). For example, within 30 min after addition of Ni₃S₂ (high dose) to cell cultures, 12.5% of the cells contained nickel particles in the cytoplasm. Within 6 hr, 75% of the cells had engulfed Ni₃S₂ particles. Cultures exposed to NiS under similar conditions had less than 1.0% of the cells containing particulate nickel within 6 hr. The uptake of Ni₃S₂ was related to the particle concentration and duration of exposure. Concentration-dependent morphological transformation was induced by Ni₃S₂ in Syrian hamster embryo cells, but similar treatment of cells with amorphous NiS resulted in no morphological transformation. Pretreatment of Syrian hamster embryo cells with benzopyrene enhanced the cellular uptake of Ni₃S₂ particles and also the incidence of Ni₃S₂-induced morphological transformation. Our results suggest that the carcinogenic activity of particulate Ni₃S₂ is related to its cellular uptake.

¹ Sponsored by Research Grants ES-02254 and ES-02487 from the National Institute of Environmental Health Sciences.

² To whom requests for reprints should be addressed, at Division of Toxicology, P. O. Box 20708, University of Texas Medical School at Houston, Houston, Texas 77025.

Received 1/11/80. Accepted 4/17/80.