Free cadmium activity in renal epithelial cells is enhanced by Mg2+ depletion.

Free Cd2+ uptake was determined by fluorescence techniques with the use of mag-fura-2 in single epithelial MDCK cells. Cytosolic Cd2+ increased in a time-dependent and concentration-dependent manner following the addition of cadmium to the external solution. The increment in cytosolic Cd2+ was greater in magnesium-depleted cells relative to normal cells. Uptake in normal and magnesium-depleted cells was inhibited by the channel antagonist, verapamil, and increased with the agonist, Bay K 8644. These studies indicate that free Cd2+ may exist in the cell cytosol and Cd2+ uptake is greater following magnesium-depletion. These data support the notion that magnesium may provide a cytoprotective effect in cadmium toxicity.