Protective effect of molybdenum on the acute toxicity of mercuric chloride. III.

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Abstract
In order to gain a better understanding of the protective mechanism of Na2MoO4 against the acute toxicity of HgCl2 in rats, turnover of 35S-Cys in the liver and kidney cytosols of rats given HgCl2 (0.03 mmol/kg, once, s.c.) with or without Na2MoO4 pretreatment (1.24 mmol/kg, once a day for 3 days, i.p.) was investigated, together with lactic dehydrogenase (LDH) activity and Hg content in the cytosols. In the liver cytosol, there was no appreciable difference in the radioactivity of 35S-Cys incorporated into the high MW (HM) fraction at various times between Hg-dosed and Mo-Hg-dosed groups, but that incorporated into the metallothionein-like (MT) fraction was higher in Hg-dosed rats than in Mo-Hg-dosed rats. In the kidney cytosol, the radioactivity of 35S-Cys was considerably higher in Mo-Hg-dosed rats than in Hg-dosed rats in all fractions including the MT fraction. The radioactivities of 35S-Cys incorporated into HM and MT fractions of liver and kidney cytosols decreased more rapidly in Mo-Hg-dosed rats than in Hg-dosed rats. The rate in decrease in LDH activity observed in the liver and kidney cytosols after exposure to HgCl2 was smaller in Mo-Hg-dosed rats than in Hg-dosed rats, although there was no difference in Hg content of HM fraction in the cytosols of these tissues at the same time point between the two groups. Na2MoO4 may alleviate the acute HgCl2 toxicity by affecting the metabolism of Cys-containing proteins, including metallothionein-like protein, in the liver and kidney cytosols.