[Cadmium-induced cytotoxicity and intracellular Ca2+ alteration in hepatocytes and protection by selenium]

Cadmium (Cd)-induced cytotoxicity and intracellular Ca2+ alteration ([Ca2+]i) in hepatocytes and intervention with selenium (Se) were studied to discuss mechanism of Cd-induced hepatocyte injury and protective effect by Se. Freshly primary culture hepatocytes isolated from neonatal mice were randomly divided into a normal control group, four treatment groups with cadmium chloride (CdCl2,5,25,100,250 micromol/L, respectively), two treatment groups with sodium selenite (Na2SeO3,10,20 micromol/L, respectively), and eight treatment groups with CdCl2 (5,25,100, 250 micromol/L,respectively) of administered Na2SeO3 (10,20 micromol/L, respectively). Hepatocyte viability and its malondialdehyde (MDA) content as well as lactate dehydrogenase (LDH) activity in cultured medium were assayed, and the intracellular free Ca2+ level ([Ca2+]i) in hepatocytes was detected with laser scanning confocal microscope (LSCM) at 12 h after treatment. The results showed that hepatocyte viability significantly decreased in Cd-exposed groups with dosages, and had no significant differences in Se-treated groups compared with that of control group. Administration of Se increased or obviously raised the viability in Cd-exposed hepatocytes. We observed a dose-dependent increase of LDH activity and significantly higher values in cultured medium of 100 and 250 micromol/L CdC12 groups compared with that in control group,while Se-treated groups had no significant change. LDH activity of administered Se in 25,100,250 micromol/L CdCl2 groups decreased or significant decreased, respectively. Different dosages of Cd induced significant elevation of MDA concentration in hepatocytes, but administration of Se to hepatocytes is incapable of eliciting the same consequences as Cd. 10 and 20 micromol/L Na2SeO3 inhibited or significantly reduced MDA production in hepatocytes induced by 25,100 and 250 micromol/L CdCl2, respectively. [Ca2+]i fluorescence intensity was significantly higher in Cd-exposed hepatocytes than in control cells and showed a dose-dependent manner,however, [Ca2+]i level of administered Se in hepatocytes was not enhanced and near to that of control cells. [Ca2+]i level of administered Se in Cd-exposed hepatocytes greatly decreased compared with Cd-exposed cells and significantly lower values of administered Se in 25 micromol/L CdCl2-exposed hepatocytes were observed and near to that of control cells. These results suggest that Cd induce cytotoxicity and damage as well as [Ca2+]i elevation in hepatocytes. Se can relieve the process of cytotoxicity and damage by intervening lipid peroxidation,improving and protecting [Ca2+]i homeostasis in Cd-induced hepatocytes.