Mercury intake by inflammatory phagocytes: in vivo cytology of mouse macrophages and neutrophils by X-ray elemental microanalysis coupled with scanning electron microscopy.
Phagocytes remove and store mercury (Hg) that enters the body. Macrophages and granulocytes respond in opposite ways to Hg: macrophages loose cell viability, and neutrophils become protected from apoptosis. We have investigated the cytology of early intake of Hg by macrophages and neutrophils after a short period (2-4 min) of in vivo exposure to HgCl2. The two types of phagocytes were attracted either to a subcutaneous air pouch or to the peritoneal cavity of BALB/c mice by in situ BSA injection. BSA caused, 72 hours later, inflammatory exudates where neutrophils (air-pouch cavity) or macrophages (peritoneal cavity) were the predominant cell type. A lethal dose of HgCl2 (25 mg) was then injected in the two inflammatory cavities. The mice died 2-4 min later and the cell exudates were harvested and studied by scanning electron microscopy coupled with X-ray elemental microanalysis (SEM-XRM). More than half of the phagocytes showed ingested Hg; a higher percentage of macrophages (around 70%) than neutrophils (around 50%) were positive for the metal. Intracellular particles of Hg were spheroid and presented a small diameter (less than 20 nm). They could be seen in large numbers inside phagocytes (up to 20-30 Hg dots per cell); they were scattered throughout the cytoplasm of the cells. The ability of phagocytes to ingest Hg increased as the BSA-induced inflammation progressed. We conclude that (i) Hg is quickly ingested as small particles by phagocytes; (ii) endocytosis of Hg increases with the degree of activation of phagocytes; and (iii) phagocytes internalize Hg by pinocytosis.
Cunha
Elisabete M
EM
Department of Anatomy, ICBAS (Abel Salazar Institute for Biomedical Sciences), University of Porto, 4099-003 Porto, Portugal. mcunha@icbas.up.pt
Oliveira
Maria João R
MJ
Ferreira
Paula G
PG
Aguas
Artur P
AP
D000818:Animals; D004577:Electron Probe Microanalysis / Q000379:methods; D005260:Female; D017737:Macrophages, Peritoneal / Q000378:metabolism* / Q000648:ultrastructure*; D008627:Mercuric Chloride / Q000378:metabolism*; D008628:Mercury / Q000032:analysis*; D051379:Mice; D008807:Mice, Inbred BALB C; D008855:Microscopy, Electron, Scanning / Q000379:methods; D009504:Neutrophils / Q000378:metabolism* / Q000648:ultrastructure*; D010587:Phagocytosis / Q000502:physiology; D010873:Pinocytosis / Q000502:physiology
D008627:Mercuric Chloride; D008628:Mercury