Thimerosal (ThM) resistant bacteria isolated from the scum of discarded vaccines containing ThM were identified as Pseudomonas sp. on the basis of its bacteriological properties. The isolated bacteria were resistant to 1165 μg/ml of ThM and also to 200 μg/ml of mercuric chloride (MC). By incubation of a mixture of ThM and the bacteria, mercury decreased from the supernatant of the culture. ThM incorporated by the bacteria could neither be dialyzed by cysteine equilibrium dialysis nor be detected by a dithizone method. After formalin treatment, the bacteria could not incorporate ThM. ThM, therefore, may be incorporated actively by the bacteria. In the case of MC, however, most of MC seems to be adsorbed on the cell surface immediately after its addition in contrast to ThM. Then incorporared ThM might be localized near the surface of the cell wall, and then enzymatically decomposed to vaporizable form, since the total mercury decreased in the reaction mixture with an increase in inorganic mercury. When sodium selenite (Se), equivalent to ThM, was added to the reaction mixture containing ThM and Pseudomonas sp. and the mixture was incubated at 27°C, total mercury in the reaction mixture did not decrease and inorganic mercury could not be detected in the suspension. It was presumed that Se may bind to inorganic mercury in the existence of cell components, and that it may prevent from vaporizing mercury from the suspension.

抄録全体を表示

The accumulation and clearance of mercury and selenium in the various tissues of rats injected with mercuric chloride and/or sodium selenite were studied. The concentrations of mercury and selenium in the blood of rats receiving both elements decreased with time and reached the blood levels of untreated rats about 56 days after dosing. Clearance rates of mercury and selenium in the liver and spleen were much lower when administered simultaneously than when administered alone. The same phenomenon was found on clearance rate of selenium in the kidney. However, the clearance rate of mercury in the kidney of rats injected with both mercury and selenium approximately agreed with that in the kidney of rats receiving mercury only between 14 and 112 days after administration. The molar ratio (Hg/Se) in the kidney of rats receiving both elements was much greater than 1 during the 112 days observation period. The results of this study indicated that the mercury and selenium accumulated in the various tissues of rats by the interaction of both elements were gradually eliminated.

抄録全体を表示

The reaction mechanism of mercury with selenium in the plasma of rats simultaneously injected HgCl₂ and Na₂SeO₃ was investigated. Sera collected after independent or simultaneous injection of HgCl₂ (10 μmol/kg, i.p. or i.v.) and Na₂SeO₃ (10 μmol/kg, s.c.) were chromatographed on Sephadex G-200 column. Distribution of mercury and selenium in the serum protein fractions of each injection group was determined by atomic absorption analysis and neutron activation analysis. On the other hand, bovine serum albumin, reduced glutathione, Na₂SeO₃, and HgCl₂ were reacted as the model reaction of mercury with selenium in the plasma. The reaction product of mercury with selenium in this reaction was chromatographed on Sephadex G-200 column and compared with in vivo experimental results. These results suggested that the final reaction product of mercury with selenium in the plasma was a colloidal HgSe, formed by the following two reactions : (1) Mercury from the Hg-binding protein transfers to the Se-binding protein and forms an intermediate such as protein-S-Se-Hg⁺. (2) The Hg-binding protein reacts with the Se-binding protein and forms an intermediate such as protein-S-Hg-Se-S-protein, or selenium from the Se-binding protein transfers to the Hg-binding protein and forms an intermediate such as protein-S-Hg-Se^-. Finally, these intermediates decompose to HgSe and then it converts to colloidal HgSe by association. The latter reaction was proved to occur in the plasma after simultaneous injection of HgCl₂ (i.v.) and Na₂SeO₃ (s.c.).

抄録全体を表示

The protective effect of six selenium compounds (sodium selenite, sodium selenate, selenocystine, selenocysteamine, selenocystamine, and selenomethionine) on the acute toxicity of methylmercuric chloride on rats was compared on the basis of survival rate and body weight change. Distribution of mercury and selenium in the rat tissues 24 hr and 1 week after the simultaneous injection of methylmercuric chloride and various selenium compounds was determined by non-destructive neutron activation analysis. All of the six selenium compounds were found to have some protective effect on the acute toxicity of methylmercuric chloride. The protective effect of six selenium compounds decreased in the order of selenomethionine, sodium selenate, selenocysteamine, selenocystine, selenocystamine, and sodium selenite. Correlation between the distribution of mercury and selenium was rarely found in the animals given simultaneous injection of methylmercuric chloride and various selenium compounds. This result suggests that the protective effect of selenium is not due to the direct binding of methylmercury and selenium.

抄録全体を表示

Mercuric chloride or methylmercuric chloride was reacted with sodium selenite in the presence of bovine serum albumin (BSA) and reduced glutathione (GSH), and these reaction mixtures were injected into tail vein of rats. Distribution of mercury in the rat tissues 1, 4, 24, and 168 hr after injection of the reaction mixture was determined by atomic absorption analysis. These experimental results were compared with the distribution of mercury in rats given mercuric chloride or methylmercuric chloride with sodium selenite. Unusual accumulation of mercury in the liver and spleen was found in the group given the reaction mixture of BSA, GSA, GSH, sodium selenite, and mercuric chloride, and in those given mercuric chloride and sodium selenite. This result supports the presumption that colloidal mercuric selenide is formed in the blood by simultaneous injection, because liver and spleen have phagocytic cells that engulf colloidal foreign particles. The significant accumulation of total mercury in the brain was found in the group given the reaction mixture of BSA, GSH, sodium selenite, and methylmercuric chloride, and in the group given methylmercuric chloride and sodium selenite. This result suggests that the reaction of methylmercury with selenium occurs in blood by their simultaneous injection, and that the reaction product easily permeates the brain.

抄録全体を表示

The distribution of mercury and selenium in the tissues 15 and 30 min, and 1, 4, and 24 hr after the injection of mercuric chloride (10 μmol/kg, i.p.) or sodium selenite (10 μmol/kg, s.c.), and after simultaneous injection of mercuric chloride and sodium selenite was determined by non-destructive neutron activation analysis. The molar ratio of selenium to mercury in the tissues of animals simultaneously injected with mercuric chloride and sodium selenite was calculated from the distributions of mercury and selenium in the tissues. In the case of simultaneous injection of mercuric chloride and sodium selenite, the reaction of mercury with selenium was found to occur mainly in the blood (red cells and plasma) at an equimolar ratio. When injection of mercuric chloride preceded the injection of sodium selenite by 4 hr, the reaction of mercury with selenium was found to occur mainly in the kidneys rather than in blood at an equimolar ratio. The results of this experiment demonstrated that the reaction of mercury with selenium occured at an equimolar ratio in vivo, regardless of dose conditions and reaction sites. The reaction product of mercury with selenium in the plasma was suggested to move gradually from the plasma to the liver, kidneys, and spleen.

抄録全体を表示

白金化合物であるシスプラチンは,抗悪性しゅよう剤として最近治療に使われてきている.しかし,シスプラチンは,じん臓機能に障害を与える副作用が生じるため,毒性軽減化の機構を明らかにする必要がある.本研究では,生体中における白金の挙動を把握するため,中性子放射化分析により,白金を定量する方法について検討を行った.分析の精度並びに定量下限値を評価するために,シスプラチンを投与したラットの肝臓,じん臓及び全血の凍結乾燥試料を作製した.その結果,測定核種には,¹⁹⁹Au(3.15d)を選択し,約1ppmまでの白金を定量できることが分かった.この方法で,シスプラチンを投与したラット中の白金の体内分布を調べたところ,各臓器とも対照ラットより白金が濃縮していた.又,亜セレン酸を同時投与したラットの組織では,シスプラチン単独投与より,更に白金が濃縮していた.

抄録全体を表示

Chromosomal aberrations induced by simultaneous treatment with mercury compound and selenium compound in human lymphocyte cultures were studied. When cultures were treated with methylmercuric chloride (MMC) or mercuric chloride alone, MMC showed higher activity for chromosome damage than mercuric chloride. Regarding effects of selenium compounds on the chromosomal aberrations induced by mercury compounds, selenious acid showed a marked protection effect against chromosome breakage by MMC or mercuric chloride. However, sodium selenate enhanced the chromosome-breaking activity of MMC and mercuric chloride. On the other hand, MMC or mercuric chloride showed a protective effect against chromosome breakage by selenious acid. Mercuric chloride was more protective than MMC to human lymphocytes.

抄録全体を表示

Behavior of methylmercury and selenium in rabbit blood was investigated in vitro or in vivo after separate or simultaneous administration of methylmercuric chloride and sodium selenite. When methylmercury and selenite were simultaneously added in vitro to rabbit blood, the rate of mercury uptake by the erythrocytes was very rapid in comparison with the case where methylmercury was added alone, and a considerable degree of selenium incorporation into the erythrocytes, which usually occurred at the early stage of incubation after sole addition of selenite, was not observed. These tendencies appeared to be similar to those observed in the blood of rabbit which was i.v. administered with methylmercury and selenite simultaneously. Either gel filtration (on Sephadex G-200 or G-15) or thin-layer chromatography, however, failed to detect any change in existing states of both the elements in plasma and stroma-free hemolysate after simultaneous in vivo or in vitro administration of methylmercury and selenite.

抄録全体を表示

ミルクカゼイン,大豆濃縮タンパク質,大豆分離タンパク質およびカツオ節について,総セレン量を蛍光法によって分析し,ついでセレンの利用率および栄養有効性を,これらをタンパク質源とする飼料を用いたラットの栄養試験から検討した.
カツオ節(3.4μg Se/g protein)を除いてこれらのタンパク質源に含まれているセレンは0.34から0.60μg/g proteinの範囲であった.栄養試験の結果,肝GSH-Px活性と肝セレン蓄積量はいずれも飼料中のセレン含量に応じて変動することが明らかとなった.一方,摂取セレン量と糞中セレン排泄量,および“代謝性セレン”量より飼料中のセレンの有効性を算出してみると,カツオ節食では約50%であるのに対し,他の飼料では少なくとも75%以上であった.以上の結果は,タンパク質に含まれているセレンの有効性を判定するにあたって,タンパク質自体の消化性も重要な要因であることを示している.

抄録全体を表示

Selenium is an essential trace element and supposed to play many biological roles. It is possible that protective effect of selenium on toxicities of heavy metals such as mercury and cadmium is one of the important biological roles of this essential element. It has been observed that behavior of mercuric mercury in animals is markedly affected by administration of selenium compounds and its toxicity dramatically decreased. The possible mechanism of the interaction between selenium and mercuric mercury in animals is summarized in this review. Toxicity of methylmercury is also protected by selenium, but the mechanism has not yet been clarified. Role of glutathione peroxidase, acceleration of methylmercury degradation and formation of bis (methylmercuric) selenide, are discussed as possible mechanisms of the modification of methylmercury toxicity by selenium.

抄録全体を表示

The effects of selenium utilization on the safety of the silver amalgam were studied in the cultured L cells and mice.
(1) Silver-tin spherical alloy was triturated with mercury. The amalgam pieces were immersed immediately in the culture medium, being rolled for 3 or 4 days. In terms of ⁵¹Cr release assay and microscopic observation, the amalgam-immersed medium, the final concentration being 1.0g amalgam in 1ml medium, showed severe cytotoxicity, which was counteracted dose-dependently by the simultaneous administration of 12.5-100. μM of sodium selenite.
(2) The cytotoxicity of the amalgam was suppressed markedly by incorpor a ting 0.2wt% of selenium into the alloy. The selenium content below 0.1wt% or above 0.4wt% in the alloy was not sufficient for attenuating the amalgam cytotoxicity.
(3) The amalgam-immersed medium made from 0.2wt% selenium-containing alloy was injected intraperitoneally into the male ddY mice for 7 days, totaling 1.3g per gram of body weight. In mice receiving selenium-lacking amalgam, the behavior was inactive, the body weight did not increase and the proximal tubules of the kidneys were damaged whereas with the selenium-containing amalgam, the behavior was active, the body weight increased and the renal tissues were not impaired. The hepatocytes were damaged in the mice receiving amalgam, which contained or lacked selenium.
(4) The toxicity of the silver amalgam was decreased markedly in the cultured L cells and mice when selenium was added to the alloy.

抄録全体を表示

The protective effect of six selenium compounds (sodium selenite, sodium selenate, selenocystine, selenocysteamine, selenocystamine, and selenomethionine) on the toxicity of mercuric chloride to rats was compared on the basis of survival rate, body weight change, and renal damage. Twenty-four hours after one of six selenium compounds was injected with mercuric chloride in rats, distribution of mercury and selenium in the tissues was determined by nondestructive neutron activation analysis. The protective effect of six selenium compounds on the toxicity of mercuric chloride decreased in the order of sodium selenite, sodium selenate, selenocystine, selenocysteamine, selenocystamine, and selenomethionine. Injection of the six selenium compounds characteristically altered the distribution of mercury in the rats and markedly increased the whole-body retention of mercury. The molar ratio of selenium to mercury in the tissues of animals simultaneously injected with mercuric chloride and selenium compound was nearly 1 : 1, except in a few cases. The result of this experiment demonstrated that mercury reacted peculiarly with selenium at an equimolar ratio in vivo and was transformed to a compound with lower toxicity. The difference in the protective effect among sodium selenite, sodium selenate, selenocystine, and selenomethionine on the toxicity of mercuric chloride was found to be explicable from the distributions of mercury and selenium, and the ratio of selenium to mercury in the tissues.

抄録全体を表示