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

Abstract

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...

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.

“…Table 5 shows numerical values of this coefficient calculated from our data. These results indicate that values bDetermined as 203Hg (51,52). cDetermined by AAS according to Balcerska et al (64).…”

“…The effect of interaction between the alkylmercurials and sodium selenite (depends on the molar Hg:Se ratio) is found to consist of a change of the distribution and therefore of concentrations of total mercury (51,52) and both its forms in individual tissues ( Table 2 and 3). However, no significant differences in the percent contribution of inorganic mercury to the total mercury content in the tissues were found between animal groups poisoned with alkymercurials alone and those receiving sodium selenite in addition to mercury (Fig.…”

“…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 methyland ethylmercuric chloride in rats in the presence and absence of selenium. the present study was designed to determine if there is a relationship between the amount ofinorganic mercury liberated from these alkylmercurial compounds in the presence and absence of selenium and the concentration of metallothionein proteins and endogenous copper in some rat tissues.…”