The influence of selenium on the level of mercury and metallothionein in rat kidneys in prolonged exposure to different mercury compounds

The effect of sodium selenite administered intragastrically in repeated doses to rats receiving ethylmercuric chloride po in various repeated doses (0.25 or 2.5 mg Hg/kg) on the excretion, whole-body retention, and organ distribution of mercury was studied.Selenium was found to affect the distribution of ethylmercury among tissues and subcellular fractions of the kidneys and liver as well as its binding to proteins of soluble fractions in these organs.Similarities and differences between the effect of interaction of sodium selenite with ethylmercuric chloride and methylmercury as well as inorganic mercury are also discussed. IntroductionEmployment of alkylmercury compounds, especially methylmercurials, in agriculture has resulted in several epidemic intoxications of humans (1)(2)(3)(4). Ethylmercuric compounds are believed to be generally less toxic due to more rapid clearance (5,6). However, these compounds have been used for a long time not only in agriculture (1, 7) but also as antiseptics, among others for preservation of blood plasma (8).Numerous poisonings by ethylmercurials have been noted, however, in humans (9-13) and in animals (14,15 and concern mainly single-dose experiments (5,10,(16)(17)(18)(19)(20)(21). On the other hand, for estimation of chronic toxicity of alkylmercury compounds, of primary importance is the extent of their accumulation in the body, determined by the magnitude and duration of exposure, uptake rate, biotransformation efficiency and excretion rate.Moreover, in the last decade considerable information has been gained on the detoxifying role of sodium selenite in experimental poisoning of animals with mercuric chloride (22-28) and methylmercury (28-35).According to some authors, in the case of mercuric chloride the mechanism of the detoxifying action of selenium involves a decrease in the renal level of mercury, and therefore a diminution of the nephrotoxic effect (22,24,29,36), the effect of selenite depending on its concentration as well as on the time and kind of exposure (37)(38)(39)(40)(41)(42).Results of studies on the mechanism of protective action of selenium in poisoning by methylmercury 131 compounds are equivocal and sometimes contradictory (27,43 At 24 hr after administration of the last dose of ethylmercuric chloride, rats were sacrificed under ether narcosis by heart puncture and then appropriate organs and tissues were removed.Mercury was estimated directly by a radiochemical method from measurement of gamma-radiation in a USB-2 scintillation counter with a NaI/Tl crystal. The time of measurement was 100 sec.Liver and kidneys were fractionated at a temperature of 0-4°C. The organs were homogenized in 7 volumes of 0.25M sucrose + 0.01% NaOH (pH 7.0) in a glass homogenizer (44). The homogenates were ifitered through a gauze and centrifuged twice at 600g for 15 min to sediment the nuclear fraction (N). The postnuclear supernatant was centrifuged twice at 7000g for 15 min to sediment the mitochondrial fraction (M). The postmitochondrial supernatant was centrifuged once a...

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“…Apart from the soluble fraction in the kidneys, Environmental Health Perspectives (37,40,(51)(52)(53).…”

Section: Resultsmentioning

confidence: 99%

Interaction of Alkylmercuric Compounds with Sodium Selenite. I. Metabolism of Ethylmercuric Chloride Administered Alone and in Combination with Sodium Selenite in Rats

Brzeznicka¹,

Chmielnicka²

1981

Environmental Health Perspectives

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“…This phenomenon is accompanied by about a fivefold diminution of mercury concentration in the kidneys and inhibition of metallothionein biosynthesis (26,27,(64)(65)(66). Simultaneously a distinct, about fourfold increase of the level of this metal is observed, especially in the mitochondrial and nuclear fractions (26) and concentration of mercury in the blood increases considerably (25,27,67).…”

Section: Discussionmentioning

confidence: 99%

Interaction of Alkylmercuric Compounds with Sodium Selenite II. Metabolism of Methylmercuric Chloride Administered Alone and in Combination with Sodium Selenite in Rats

Brzeznicka¹,

Chmielnicka²

1985

Environmental Health Perspectives

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“…An increase in the concentration ofmetallothioneinlike proteins, highly correlated with the level of inorganic mercury, was observed after prolonged exposure of rats to ethylmercuric chloride and methylmercuric Tanoguanidine (48). It was also demonstrated that Me 03Hg (49,51), methoxyethyl 203Hg (49) and Et203Hg (52) are bound by low molecular weight proteins of the soluble fraction of rat kidneys.…”

Section: Introductionmentioning

confidence: 78%

“…The presence of selenium inhibits the stimulation of biosynthesis of metallothioneinlike proteins by inorganic mercury (47,48,(59)(60)(61)(62)(63). Our previous studies (51,52) have dealt with the metabolism of methyl-and ethylmercuric chloride in rats in the presence and absence of selenium.…”

Section: Introductionmentioning

confidence: 99%

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Interaction of alkylmercuric compounds with sodium selenite. III. Biotransformation, levels of metallothioneinlike proteins and endogenous copper in some tissues of rats exposed to methyl or ethylmercuric chloride with and without sodium selenite

Brzeźnicka¹,

Chmielnicka²

1985

Environ Health Perspect

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The biotransformation efficiency of alkylmercurial compounds was studied in rat liver, kidneys, blood, and brain after 2-week administration of methylmercuric chloride (MeHg) and ethylmercuric chloride (EtHg) at doses of 0.25 or 2.5 mg Hg/kg, alone or in combination with sodium selenite (Se) at a level of 0.5 mg Se/kg. Simultaneously, the level of metallothioneinlike proteins (MTP) and endogenous copper (Cu) was monitored in tissues of control rats and intoxicated rats.Regardless of the dose, the highest concentrations of inorganic mercury from both the alkylmercurials was found in the rat kidneys. Sodium selenite had a variable effect on the amount of inorganic mercury liberated, depending on the organ and the molar ratio of Hg:Se administered.A statistically significant increase in the levels of MTP and endogenous Cu, compared with control group, was found only in the kidneys of intoxicated rats. This increase was dependent on the concentration of inorganic mercury liberated by biotransformation of alkylmercurials. The observed changes appeared when the level of inorganic mercury exceeded 10,Ig Hg/g tissue and reached a plateau at about 40 ,ug Hg/g tissue. In the presence of selenium the plateau of MTP and Cu levels were no oberved in the kidneys, regardless of the amount of inorganic mercury liberated.

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The influence of selenium on the level of mercury and metallothionein in rat kidneys in prolonged exposure to different mercury compounds

Cited by 35 publications

References 19 publications

Interaction of Alkylmercuric Compounds with Sodium Selenite. I. Metabolism of Ethylmercuric Chloride Administered Alone and in Combination with Sodium Selenite in Rats

Interaction of Alkylmercuric Compounds with Sodium Selenite. I. Metabolism of Ethylmercuric Chloride Administered Alone and in Combination with Sodium Selenite in Rats

Interaction of Alkylmercuric Compounds with Sodium Selenite II. Metabolism of Methylmercuric Chloride Administered Alone and in Combination with Sodium Selenite in Rats

Interaction of alkylmercuric compounds with sodium selenite. III. Biotransformation, levels of metallothioneinlike proteins and endogenous copper in some tissues of rats exposed to methyl or ethylmercuric chloride with and without sodium selenite

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