Dimethylarsinic acid urine excrete

Dimethylarsinic acid is the major metabolite of orally administered arsenic trioxide, and is excreted rapidly in the urine (Yamauchi and Yamamura 1985). The methylation process is true detoxification, since methanearsonates and cacodylates are about 200 times less toxic than sodium arsenite (NAS 1977). The marmoset monkey (Callithrix jacchus), unlike all other animal species studied to date, was not able (for unknown reasons) to metabolize administered As+5 to demethylarsinic acid most was reduced to As+3. Only 20% of the total dose was excreted in urine as unchanged As+5, and another 20% as As+3. The rest was bound to tissues, giving distribution patterns similar to arsenite (Vahter and Marafante 1985). Accordingly, the marmoset, like the rat, may be unsuitable for research with arsenicals. 

Inorganic arsenic is methylated in humans to monomethylarsonic acid, MMA(V), and dimethylarsinic acid, DMA(V), both of which are more rapidly excreted in urine than is inorganic arsenic - especially the trivalent form (As III, arsen-ite). Absorbed arsenate (As V) is reduced to trivalent arsenic (As III) (for a review, see Vahter 2000). Le etal. (2000a,b) also identified monomethylarsonous acid, MMA(III), in the urine of inhabitants from irmer Mongolia after a single oral administration of 300 mg sodium-dimercapto-l-propane sulfonate (DMPS). 

There have been many studies on arsenic species in human urine, and these data are covered in other parts of this book. The arsenic species present in urine depend largely on the diet, and some compounds contained in seafood (e.g., arsenobetaine) are excreted essentially unchanged (12). Ingested inorganic arsenic is in part methylated and excreted as methylarsonate and dimethylarsinate in addition to arsenite and arsenate (12). Interesting new urine metabolites are methylar-sonous acid and dimethylarsinous acid (133). These compounds had been reported earlier in lake water (68). 

The main excreted forms are dimethylarsinic acid (DMA ) and methylarsonic acid (MA ) in addition, several minor arsenic compounds can be found in urine depending on the amount of ingested arsenic... 

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