In vivo ingestion of heavy metal particles of Se, Hg and W by murine macrophages. A study using scanning electron microscopy coupled with X-ray microanalysis

Abstract

Several heavy metals that are currently employed in industry may become polluters of work and natural environments. As particulate matter, heavy metals are suitable for entering the human body through the respiratory and digestive systems. They often end up inside phagocytes; the size of the microscopic particles modulates both their phagocytosis, and the physiology of macrophages. Here we have adopted an experimental model to investigate the ingestion of particles of three industrial heavy metals (Se, Hg, W) by murine peritoneal macrophages in vivo. The phagocytes were studied by scanning electron microscopy coupled with X-ray elemental microanalysis (SEM-XRM), a method that allows specific identification of Se, W and Hg in cells at high resolution. We found that Hg that was taken up by macrophages was organized into small, round particles (0.31 +/- 0.14 microm). This was in contrast with the larger size of intracellular particles of Se (2.37 +/- 1.84 microm) or W (1.75 +/- 1.34 microm). Ingested particles of Se and W, but not Hg, often caused bulging of the cell surface of macrophages. We conclude that particulate matters of Se, W and Hg are organized in particles of different size inside macrophages. This size difference is likely to be associated with distinct phlogistic activities of these heavy metals, Se and W causing a milder inflammatory reaction than Hg.

In Vivo Formation and Binding of SeHg Complexes to the Erythrocyte Surface

“…In liver samples of mice that were intraperitoneally injected with the Hg salt alone, we have detected heavy labeling of the erythrocyte surface by Hg-positive particles (Fig. 2), as we have described before [7][8][9][10]. Injection of Se salt alone failed to label the surface of liver erythrocytes with Se-positive particles.…”

“…The protective effect of selenite on the toxicity of Hg in mammals derives from the formation of stable and inert complexes of mercuric selenide, SeHg [4][5][6]. We have used here electron microscopy to investigate the in vivo interaction between Se and Hg since we had previously documented that it is possible to obtain high-resolution identification of Hg particles in tissues and cells by the use of scanning electron microscopy coupled with X-ray microanalysis (SEM-XRM) [7][8][9][10]. The same technical approach was now used for the simultaneous detection of Hg and Se on the surface of mouse erythrocytes.…”

“…For that, we have injected Hg and Se salts, together or in separate, and at different timings, in the peritoneal cavity of mice. Because we had found before that, within a few minutes of Hg injection, the surface of erythrocytes was labeled by Hg [7][8][9][10], we have used this phenomenon to test whether a fast formation of SeHg complexes does occur in vivo, and under which conditions does it happen.…”

Mouse Monocytes (RAW CELLS) and the Handling of Cysteine and Homocysteine S-Conjugates of Inorganic Mercury and Methylmercury

“…Asterisk indicates significantly different (p < .05) from the mean for the corresponding group of RAW cells exposed to CH 3 Hg-Cys in the presence 140 mM N-methyl-D-glucamine. All Cells Were Exposed to 5 μm CH 3 Hg-Hcy mercury-containing particles by pinocytosis (Cunha et al, 2004: Cherdwongcharoensuk et al, 2002. Several investigators have demonstrated that when certain metal species, including those of mercury, are taken up by monocytes/macrophages, they alter significantly metabolic activity in the cells Noda et al, 2002).…”

“…Unfortunately, very little is known about the mechanisms by which mercuric ions gain entry into monocytes and macrophages. There are some data indicating that phagocytic cells can take up mercuric species by endocytosis (Cunha et al, 2004;Cherdwongcharoensuk et al, 2002). However, very little else is known about the mechanisms by which monocyte/macrophages can take up mercuric species.…”