Chromium complexes mutagenicity

The way in which the dominant reduction mechanism for chromate changes with the reaction conditions and how this is related to the toxicity of chromate is not as yet clear. As outlined above, the products of the reaction may depend on the mechanism of reduction and these, as yet, unidentified chromium complexes are probably the agents responsible for the mutagenicity of chromate. The substantial stability of the chromium(V) complexes and thiolate esters generated in the reaction of GSH with chromate suggests that if similar complexes were formed in vivo they would have time to reach many intracellular compartments and could hence be the crucial active intermediates in the toxicity of chromate. 

Chromium Complexes. Table IV contains the results on chromium compounds. Like rhodium, a ais dihalo structure seems to confer mutagenic properties on the complex. Unlike the rhodium complexes, no activity is observed in the ois dihalopolyamine complexes. Several other complexes are active too, but these undergo sufficiently rapid ligand exchange that we are unsure as to the... 

Little is known about DNA damage by Cr(III) complexes, even though these compounds are considered to be responsible for chromium mutagenicity. The [Cr (phen)2Cl2] Euid [Cr (bpy)2Cl2] complexes are both mutagenic and able to cleave a supercoiled plasmid DNA via ss breaks, whereas [Cr (CN)e] is not mutagenic and is inefficient as a DNA cleaver 162). 

The carcinogenicity and mutagenicity of chromium(VI) are well established.The toxicity is usually considered in terms of the uptake/reduction modeP since chromium(VI) readily passes into the cell, via anion channels, and once within the cell it is eventually reduced by cellular components to chromium(III) species. Figure 6 illustrates the likely fate of chromate within a mammalian cell. As can be appreciated from Figure 6 it is complexes trapped within the cell that are the agents responsible for the toxic effects of chromate. The systems which reduce the chromiumfvi) are as yet unknown, as are the final products of the reaction. However, microsomes are capable of reducing chromium(VI) as are various nucleotides and even fulvic acids.In these cases chromium(V) species of considerable stability have been observed using EPR spectroscopy. Within the cell reduction by a sulfide is the most probable reaction. 

Over a decade ago, Sugden et al. (211) showed that the Cr(lll) complex, [Cr(bpy)2Cl2], was mutagenic in several S. typhimurium strains only under aerobic conditions. Chromium(Vl) induced mutagenicity was O2 dependent in... 

The mutagenicity of chromium(III) complexes suggests that they could be responsible for the high incidence of lung cancer noted for chromium workers. 

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