RESUMO
The risks of metals for health are highlighted by their chemical stability and their persistence in the environment. Chronic exposure to low cadmium (Cd) concentrations results in renal dysfunction mainly. Cd has been regarded primarily as a renal tubular toxicant, but glomerular structures may also be affected. Since the cellular environment may influence metal toxicity, differences concerning Cd uptake and toxicity were evaluated according to calcium (Ca) medium concentrations. An optimized inductively coupled plasma emission spectrometry method (ICP/OES) was developed under defined conditions, as a selective analytical tool to determine cadmium uptake in glomerular mesangial cells. The performance characteristics of the analytical system were evaluated for both Cd and Ca by calibration (50 to 250 microg/L and 1 to 5 mg/L), linearity (r2 .9968 and .9943), limits of detection (1 microg/L and 0.1 mg/L) and quantitation (3 microg/L and 0.3 mg/L), accuracy with spiking, and repeatability (1.2 and 2.9%) with matrix matched standards. Total intracellular Cd content was significantly threefold lower in 0.175 mM Ca medium (Ca-free Eagle's minimum essential medium [EMEM] medium with 5% fetal bovine serum [FBS]) than in EMEM medium (1.8 mM Ca) with respectively 0.16 and 0.37 microg/mg proteins after 24 h of Cd (1 microM) exposure. Similar differences were obtained in cytotoxicity studies with a fourfold reduction in the mortality index (IC50). Complementary assays using Ca-spiked medium reinforced that Cd cytotoxicity and uptake were significantly dependent on the concentration of extracellular Ca. These findings suggest direct link between Cd uptake and toxicity, underlining the relevance of the analytical method.
