The role of Ca2+ in cadmium-induced renal tubular cell injury.

Changes in rat renal proximal tubule cell gene expression were studied in vitro using a cadmium metallothionein (CdMT) exposure model. Increased expression of MT together with alterations in the expression of several other stress protein products were demonstrated by 35S-two-dimensional gel electrophoresis. Stress proteins with estimated molecular masses of 32, 70 and 90 kDa were observed to be increased after 4 h of exposure. These changes preceded the onset of cell injury. Internal stores of Ca2+ were not found to be measurably altered, as measured by the changes in fluorescence of the dye FURA-2. These data suggest that the observed alterations in gene expression are directly mediated by Cd2+ and not secondary to increased availability of Ca2+ within the target cell population, perhaps mediated by the transacting factor which regulates MT synthesis. The calcuria resulting from in vivo exposure to Cd2+ in workers or CdMT exposure in animal models may be secondary to alterations in renal proximal tubule cell gene expression.