Arsenic Table arsenobetaine

Uptake experiments have also been conducted with other forms of arsenic. M. edulis exposed separately to a number of organoarsenic compounds in seawater were found to be selective in their arsenic uptake (85). They did not accumulate arsenic when it was present as MMA, DMA, TMAO, or DMAE. When exposed to the three quaternary arsonium compounds (arsenobetaine, arsenocholine, and TeMA), however, the mussels accumulated substantial quantities of arsenic, with arsenobetaine being the most efficiently accumulated (Table VII). The chemical form of the accumulated arsenic was also examined. Mussels... 

Arsenobetaine was the first arsenic compound identified in a marine animal when it was isolated in 1977 in a crystalline form from the tail muscle of the western rock lobster Panulirus cygnus (48). The large body of work that followed established that arsenobetaine was by far the predominant form of arsenic in marine animals (Table VI). It occurs at all trophic levels, although there is a tendency for it to be present at higher concentrations (or at least constitute the greater percentage... 

It is of interest that arsenobetaine is accumulated so much more readily than other similar arsenic species. The cationic nature of the compounds may be significant those compounds not bioaccumulated by the mussel are all anionic or neutral at seawater pH, whereas those accumulated all contain a positive charge. The zwitterionic nature of arsenobetaine may also be a factor, and recent experiments with C-3 and C-4 arsenic containing betaines (compounds 42 and 43) support this view. Preliminary results (164 ) show that mussels bioaccumulate these compounds readily the relative bioaccumulation efficiency was C-2 betaine (arsenobetaine) 100, C-3 betaine 65, and C-4 betaine 6 (Table VII). These results also suggest that the distance between the charges in the molecules may be an additional factor. Expansion of studies on arsenic uptake from water may elucidate the actual processes of absorption of arsenobetaine, which may involve a specific ion channel. 

Total arsenic as well as arsenobetaine and dimethylarsinic acid had to be quantified. Inorganic species (As(III) and As(V)), as well as arsenocholine and monomethylarsonic acid were not detected by the various methods described in Table 7.8. 

Arsenic occurs in many chemical forms in the environment, i.e. arsenite As(m), arsenate As(v), monomethylarsonic acid (MMAA), dimethylarsinic acid (DMAA), arsenobetaine (AsB) and arsenochloine (AsC) (Table 5.5), with a... 

The dominant organoarsenic compounds in aquatic systems are (CHj) 3AS CH2. COO (arsenobetaine) and (CH3)3AS CH2CH20H (arsenocholine). The arsenic concentration of hsh and marine invertebrates differs widely depending on the species and the organ under consideration (Table 1). 

Table 2 summarizes literature data on arsenic species in blood. Limited speciation analyses revealed the presence of arsenobetaine (AB) and DMA(V) in human blood (106-108). Arsenobetaine and DMA(V) were detectable in serum of uremic (renal disease) patients, with mean values being 1 pg/L for DMA(V) and... 

Acute toxicity decreases in the following order As(III) > As(V) > MAA > DMAA, suggesting that the acute toxicity of arsenic compounds diminishes with progressive methylation. Arsenobetaine [22], arsenocholine [23], trimethylarsine oxide [24], DMAA [24], MAA [24], and As(III) [22] have so far been fed to mice to estimate their toxicities, as summarized in TABLE 1. For arsenobetaine, the most ubiquitous arsenical in marine animals, an acute LD50 cannot be obtained because arsenobetaine administered orally to mice at a dose of 10 g per kg of body weight did not cause any toxic symptoms. The other trimethylated compounds, arsenocholine and trimethylarsine oxide, are 200 to 300 times less toxic than arsenic trioxide. 

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