COMPARISON OF THE URINARY METABOLITES OF RATS, MICE AND HUMANS AFTER ORAL ARSENIC EXPOSURE FOCUSING ON THIOARSENICALS

摘要

Urinary metabolites of arsenic are useful as biomarkers of exposure because ingested arsenic is excreted primarily in urine. The pattern of metabolism depends upon the arsenical which is ingested. For example, both arsenosugars and inorganic arsenic generate dimethylarsinate as a major urinary metabolite. For arsenosugars, this involves cleavage of As-C bonds; for inorganic arsenic, As-C bonds are formed. These transformations occur by different pathways. In comparison, other arsenicals such as arsenobetaine and arsenocholine are excreted unchanged in urine. Complete urinary arsenic speciation can provide insight into possible metabolic pathways as well as potential exposure sources. The recent finding of sulfur analogs of some arsenic oxides indicates that comprehensive urinary speciation has not yet been achieved. It is with this in mind that a series of urine samples from rats, mice and humans have been analyzed specifically for the thiolated arsenicals dimethylthioarsinic acid (DMTA) and trimethylarsine sulfide (TMAS). The urine samples analyzed were previously collected as part of three unique investigations with different arsenic exposures. The results are compiled here as an overview of the thio-arsenicals detected in urine. These analyses were performed knowing that thio-arsenical formation was possible during sample preparation and handling, similar to previously reported studies of such transformations.