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Distribution of vanadium

1986 
To gain insight into the cellular vanadium accumulation and distribution the authors measured VO/sup 2 +/ binding to intracellular ligands in vitro and calculated free and bound VO/sup 2 +/ for different ligands and VO/sup 2 +/ concentrations that may be encountered in cells. The strong binding of VO/sup 2 +/ to phosphates is, at least in part, the basis for intracellular accumulation of vanadium. Free intracellular VO/sup 2 +/ concentration should be on the order of 10/sup -10/-10/sup -19/ M (<1% of 10/sup -8/ M to 4 x 10/sup -7/ M or 0.5-20 ng vanadium/g). Such low concentrations of VO/sup 2 +/ do not affect enzymes or functions studied so far. The estimate of free intracellular VO/sub 3//sup -/ concentration of 3 x 10/sup -11/ M is below the 4 x 10/sup -9/ M value obtained by Cantley et al. for the dissociation constant of VO/sub 3//sup -/ and the high-affinity site of the Na/sup +/, K/sup +/-ATPase molecule under optimal conditions. The value for the low-affinity site was 5 x 10/sup -7/ M. Thus, in the absence of active transport, the normal free intracellular VO/sub 3//sup -/ concentration appears to be too low for an effect on the more » Na/sup +/, K/sup +/ pump. « less
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