Uptake of chromium (III) complexes by erythrocytes

Abstract
Trivalent chromium is assumed to be the ultimate genotoxic form of Cr after uptake and reduction of chromate in cells. Cr(III) also is an essential trace element for mammalia; it is required for the proper control of glucose metabolism. In both kinds of biological effects, Cr(III) is assumed to act in the form of complexes with biomolecules, but there is very little information about the uptake of such complexes through membranes. By electrothermal atomic absorption we investigated the time course of the binding and uptake with human erythrocytes of [Cr(glycine)3], [Cr(2,4‐pentanedione)3], [Cr(glutathione)2]2‐, [Cr(Cysteine)2]1‐, [Cr(o‐phenanthroline)2Cl2]1+ and [Cr(bipyridine)2Cl2]1+. In all cases chromium was bound and taken up significantly except with the cysteine complex which bound to the cells but sedimented with the cell envelope after cell lysis. The uptake of Cr(III) compounds was very slow. At 1 mM concentrations and 1 hour at 37°C the intracellular chromium was estimated to be between 0.5 to 2.0 x 10‐18mol/cell. This corresponds to rate constants more than 3 orders of magnitude less than that of Cr(VI) uptake. We detected only a weak correlation of chromium uptake to the charge of the complexes or to the hydro‐phobicity of the ligands.