Comparative toxicology of mercurials in Caenorhabditis elegans

Mercury (Hg) is a toxic metal that can exist in multiple chemical species. Humans are commonly exposed to methylmercury and Hg vapor, which are converted to mercuric species in the body. Despite years of research, little information exists on the similarities and differences in the mechanisms of Hg toxicity. The relative toxicity of mercuric chloride (HgCl(2)) and methylmercury chloride (MeHgCl) in Caenorhabditis elegans was determined in assays that measured growth, feeding, reproduction, and locomotion. The effect of HgCl(2) and MeHgCl on the expression of several archetypal stress-response genes was also determined. There was no significant difference between the EC50s of the two mercurials in terms of C. elegans growth. However, MeHgCl was more toxic to C. elegans than HgCl(2) when assessing feeding, movement, and reproduction, all of which require proper neuromuscular activity. Methylmercury chloride exposure resulted in increased steady-state levels of the stress response genes at lower concentrations than HgCl(2). In general, MeHgCl was more toxic to C. elegans than HgCl(2), particularly when assaying behaviors that require neuromuscular function.