In vitro and in vivo uptake of nickel sulfides by rat lymphocytes.

The uptake, the biological transformation and the interaction with cellular constituents of alpha Ni3S2 and beta NiS have been studied in vitro and in vivo on rat lymphocytes. beta NiS crystals are phagocytized in vitro and no structural degradation is observed within the first 3 days of exposure. Energy dispersive spectrometry (EDS) reveals a slight dissolution characterized by the loss of sulfur. alpha Ni3S2 is degraded in the extracellular space to minute particles (50-100 nm) covering the cell membrane. Smaller intracellular particles (10-30 nm) are found selectively bound to mitochondria, endoplasmic reticulum, Golgi vesicles, nuclear membranes, and the euchromatinic part of nuclei. EDS analyses reveal that the particles bound to cell membranes and euchromatin no longer contain sulfur but phosphorus and nickel as inorganic compounds. This observation suggests the formation of a Ni/P complex with the phosphate groups either of membranous phospholipids or of nuclear RNA or DNA. A similar uptake and transformation process of alpha Ni3S2 is observed on lymphocytes after in vivo incubation. This leads us to consider lymphocytes as target cells, as compared with other cell types where the alpha Ni3S2 uptake occurs only partially. The present findings show a difference of uptake and biological transformation between alpha Ni3S2 and beta NiS. The identical results obtained after in vitro and in vivo bioassays enhance the in vitro experiments, at least for this cell type.