Increase in intracellular Cd2+ concentration of rat cerebellar granule neurons incubated with cadmium chloride:: Cadmium cytotoxicity under external Ca2+-free condition

In order to examine the cadmium cytotoxicity unrelated to external Ca2+, the effects of micromolar CdCl2 on intracellular Cd2+ concentration, cellular content of glutathione, and cell viability of rat cerebellar granule neurons were examined under normal Ca2+ and external Ca2+ -free conditions, using a laser confocal microscope with fluorescent probes, fluo-3-AM, 5-chloromethylfluorescein (CMF) diacetate, and propidium iodide. CdCl2 (10-300 mu M) dose-dependently increased the intensity of fluo-3 fluorescence. Exposure to CdCl2 equally enhanced the fluo-3 fluorescence under both Ca2+ conditions and MnCl2 did not quench the CdCl2-enhanced fluorescence. The results indicate that the enhancement of fluo-3 fluorescence is due to the increase in intracellular Cd2+ concentration. CdCl2 at 100-300 mu M decreased the intensity of CMF fluorescence, indicating the decrease in cellular content of glutathione. The population of cells stained with propidium (dead cells) was increased by 100-300 mu M CdCl2- Similar results described above were also observed under external Ca2+-free condition. It is suggested that some of cytotoxic actions of CdCl2 on neurons are unrelated to external Ca2+ one of main sources for increasing intracellular Ca concentration. (c) 2005 Elsevier Ltd. All rights reserved.