The chemical speciation, spatial distribution and toxicity of mercury from Tibetan medicine Zuotai，β-HgS and HgCl2 in mouse kidney

Zuotai , a famous Tibetan medicinal mixture containing β-HgS, has been used to combine with herbal remedies for treating diseases for more than 1 300 years. The target organ for inorganic mercury toxicity is generally considered to be the kidney. Therefore, it is crucial to reveal the chemical speciation , spatial distribution and potential nephrotoxicity of mercury from Zuotai in kidney. To date, this remains poorly understood. We used X-ray absorption spectroscopy (XAS) and micro X-ray fluorescence (μ-XRF) imaging based on synchrotron radiation to study mercury chemical forms and mercury special distribution in kidney after mice were treated orally with Zuotai , β-HgS or HgCl 2 . Meanwhile, the histopathology of kidney was observed. Mice exposed with Zuotai showed kidney with significant proportion of mercury ions bound to sulfydryl biomolecules (e.g. Cys-S-Hg-S-Cys) plus some of unknown species, but without methylmercury cysteine, which is the same as β-HgS and HgCl 2 . The mercury is mainly deposited in renal cortex in mouse treated with Zuotai , β-HgS or HgCl 2 , but with a low level of mercury in medulla. The total mercury in kidney of mice treated with HgCl 2 was much higher than that of β-HgS, and the later was higher than that of Zuotai . And, HgCl 2 cause severe impairments in mouse kidney, but that was not observed in the Zuotai and β-HgS groups. Meanwhile, the bio-metals (Ca, Zn, Fe and Cu) micro-distributions in kidney were also revealed. These findings elucidated the chemical nature, spatial distribution and toxicity difference of mercury from Zuotai , β-HgS and HgCl 2 in mouse kidney, and provide new insights into the appropriate methods for biological monitoring.