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.

Abstract

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 micrograms Hg/g tissue and reached a plateau at about 40 micrograms Hg/g tissue. In the presence of selenium the plateau of MTP and Cu levels were no observed in the kidneys, regardless of the amount of inorganic mercury liberated.

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

“…6) points to a possible participation of metallothionein-like proteins in this process (15,68). That is probably due to the higher efficiency of biotransformation of methylmercury to inorganic mercury in rat kidneys as compared with liver (58,65,69,70); this process seems to be strictly dependent on the dose of methylmercury which has been taken into account in our further studies (71).…”

The localization of mercury and metallothionein in the cerebellum of rats experimentally exposed to methylmercury

“…It is widely believed that only the inorganic mercuric ion, Hg 2+, is capable of eliciting the metallothionein response (Chmielnicka & Brzeznicka, 1978), and that, in rats dosed with methylmercury, the appearance of LEYSHON-S~RLAND, JASANI and MORGAN metallothionein within the kidney is due to the biotransformation of the alkyl mercurial to the inorganic form (Brzeznicka & Chmielnicka, 1985). In the brain, the inorganic mercury content amounted to only 15% of the total mercury accumulated in the tissue (Brzeznicka & Chmielnicka, 1985). Since Baatrup et al (1986) reported that only inorganic mercury is located histochemically by silver physical development, it would appear that a substantial level of biotransformation has taken place, at least in some cells of the cerebellum.…”