Quantification of particles of lethal mercury in mouse viscera: high-resolution study of mercury in cells and tissues

Hg- and Cd-induced modulation of lipid packing and monolayer fluidity in biomimetic erythrocyte model systems

The public health consequences that are associated with the low level exposure of various human populations to Cd(2+) and Hg(2+) are incompletely understood. In order to assess if interactions between these inorganic pollutants and erythrocyte biomembranes may contribute to their chronic toxicity, we have used a Langmuir trough to probe the effect of HgCl2 and CdCl2 on the packing and elasticity properties of biomimetic lipid monolayers using different lipid mixtures. These lipid films were deposited at room temperature on a biologically relevant subphase (1mM phosphate, 100mM NaCl at pH 7.4) in the absence and presence of 100μM HgCl2, CdCl2 and 1:1 mixtures thereof. The interactions of heavy metals with the lipids were monitored as changes in the surface pressure (π)-area (A) isotherms. In addition, metal induced changes to the elastic properties of the model systems were analyzed by area and compressibility data of phosphatidylcholine (PC) systems containing 0, 15, 30, 45 and 100% phosphatidylethanolamine (PE) and phosphatidylserine (PS). These mixtures revealed changes in lateral lipid packing as indicated by area expansion as well as enhanced film rigidity. The results demonstrate that both heavy metals affected the various lipid matrices, but metal mixtures showed the strongest impact. Based on these data, the adverse interaction of Hg(2+) and Cd(2+) with lipid bilayer membranes is identified as a feasible mechanism by which these toxic metals exert toxicity in mammalian cells. Interestingly, these metal interactions were found to depend on the lipid composition.

Placental and fetal disposition of mercuric ions in rats exposed to methylmercury: role of Mrp2

Methylmercury is a prevalent environmental toxicant that can have deleterious effects on a developing fetus. Previous studies indicate that the multidrug resistance-associated protein 2 (Mrp2) is involved in renal and hepatic export of mercuric ions. Therefore, we hypothesize that Mrp2 is also involved in export of mercuric ions from placental trophoblasts and fetal tissues. To test this hypothesis, we assessed the disposition of mercuric ions in pregnant Wistar and TR(-) (Mrp2-deficient) rats exposed to a single dose of methylmercury. The amount of mercury in renal tissues (cortex and outer stripe of outer medulla), liver, blood, amniotic fluid, uterus, placentas and fetuses was significantly greater in TR(-) rats than in Wistar rats. Urinary and fecal elimination of mercury was greater in Wistar dams than in TR(-) dams. Thus, our findings suggest that Mrp2 may be involved in the export of mercuric ions from maternal and fetal organs following exposure to methylmercury.

Lead hepatotoxicology: a study in an animal model

The increasing use of lead (Pb) for industrial purposes has resulted in the significant increase in environmental contamination of our planet especially in concern to water and food. In this study using the electron scanning microscopy (SEM), the authors showed the effects of this metal as a result of a chronic and cumulative process. As a primary method of detection of Pb in situ, SEM was chosen, coupled with a detection system Noran Voyager of basic microanalysis X-ray (SEM-XRM), with detection system energy dispersive spectrometry. Mice BALB/c was used as a study model. An animal model of inflammation was used, that consisted in the formation of a subcutaneous pocket of air. It was observed that 75% of Pb stock was captured by the liver, the main target organ in the capture of the metal, the kidney was the second organ to capture the Pb stock and the third was the spleen. It was verified that a low deposition of Pb was found in the lungs and the brain. The main results of this study showed how Pb is captured by different organs. We also demonstrated the vulnerability to inflammation of this metal.

In vivo formation and binding of SeHg complexes to the erythrocyte surface

The in vivo dynamics of selenium (Se) and mercury (Hg) interaction was studied in mouse tissues using direct visualization of individual Se, Hg, and SeHg particles on the surface of circulating erythrocytes. This high-resolution detection of Se and Hg was obtained by scanning electron microscopy coupled to X-ray microanalysis. BALB/c mice were injected in the peritoneal cavity with Se and Hg salts, and the animals were sacrificed 3 min after the Hg injection. Only a minority (9%) of the metal dots seen on mouse liver erythrocytes were SeHg complexes when Se and Hg salts were mixed together before injection. In contrast, the majority (73%) of metal dots on liver erythrocytes were SeHg complexes if Se was injected at least 5 min before Hg injection. All metal dots on liver erythrocytes were of SeHg complexes if Se was injected 9 or 12 min before the Hg injection. We conclude that the formation of stable in vivo SeHg complexes requires preliminary interaction of Se with a putative serum factor before complexes between Se and Hg are formed and are bound to the erythrocyte cell surface.

Acute depletion and recovery of peritoneal B-1 lymphocytes in BALB/c mice after a single injection of mercury chloride

The acute toxicity of mercury (Hg) to B cells was studied in the peritoneal cavity of BALB/c mice, a coelomic space where both B-1 and B-2 subsets of B lymphocytes are present. Up to 24 hr after a single in situ Hg injection, the peritoneal cavity became virtually devoid of lymphocytes, particularly of the B-1 subset. Lymphocyte depletion was more severe for B than T cells. This depletion was associated with partial lymphocyte activation (CD69(+)) at 6 hr of treatment and it was due to apoptosis rather than to necrosis. Partial recovery of both B and T cells was observed in the peritoneal cavity 48 hr after the Hg injection. The phenomenon was followed by a second decrease in peritoneal lymphocytes 72 hr after Hg. Neutrophils that entered the peritoneal cavity because of the Hg injection were resistant to apoptosis. No significant changes in lymphocyte number or subpopulation were found in the spleen and thymus of the mice up to 72 hr after the Hg treatment. We concluded that B lymphocytes were severely affected by the toxic effects of Hg. Our data suggest that Hg-induced unbalance in the repertoire of B cells, of the B-1 subset in particular, may result later in the secretion of the high titres of pathogenic autoantibodies that are found in the Hg-induced lupus disorder of BALB/c mice.