The Fate of Methylmercury Through Formation of Bismethylmercury Sulfide as an Intermediate in Mice

A previous study of ours indicated that methylmercury (MeHg) is biotransformed to bismethylmercury sulfide [(MeHg)2S)] by interaction with reactive sulfur species (RSS) produced in the body. In the present study, we explored the transformation of MeHg to (MeHg)2S in the gut and the subsequent fate of (MeHg)2S in vitro and in vivo. An ex vivo experiment suggested the possibility of extracellular transformation of MeHg to (MeHg)2S in the distal colon, and accordingly, the sulfur adduct MeHg was detected in the intestinal content and feces of mice given MeHg, suggesting that (MeHg)2S is formed from reactions of MeHg with RSS in the gut. In a cell-free system, we found that (MeHg)2S spontaneously undergoes degradation in a time-dependent fashion, resulting in formation of mercury sulfide, as determined by X-ray diffraction, and dimethylmercury (DMeHg), as evaluated by gas chromatography/mass spectrometry. We also identified DMeHg in expiration after intraperitoneal administration of (MeHg)2S to mice. Our present study therefore identifies a new fate of MeHg through (MeHg)2S as an intermediate, which leads to conversion of volatile DMeHg in the body.