Effect of molybdenum on the acute toxicity of mercuric chloride. IV. Effect of molybdenum on mercury-mediated metallothionein mRNA induction

Abstract

In order to elucidate the mechanism of the stimulative effect of molybdenum on mercury-mediated renal metallothionein induction, the levels of translatable metallothionein mRNA (MT mRNA) in the kidneys of rats treated with saline or Na 2MoO 4 or HgCl 2 or Na 2MoO 4 and HgCl 2 were measured by translation experiments in cell-free protein synthesizing systems. The time course of accumulation of mercury in renal nuclei of rats given HgCl 2 with or without Na 2MoO 4-pretreatment was also investigated. Molybdenum, itself, did not elevate levels of MT mRNA compared to saline controls at all time points (0, 6 and 14 h after exposure to HgCl 2) but rapidly elevated the levels of the mRNA more than Hg-dosed rats when HgCl 2 was also administered. On the other hand, the time course study in renal nuclei showed that the mercury content of nuclei was consistently lower in Mo-Hg-dosed rats than in Hg-dosed rats at all time points (4, 8 and 24 h after exposure to HgCl 2). These results suggest that the stimulative effect of molybdenum on mercury-mediated metallothionein induction is coupled with an increase of the mRNA coding for the low molecular weight protein and that such an increase in the levels of translatable MT mRNA is not due to the difference in uptake of mercury into renal nuclei.