A study of the biological effects of rare earth elements at cellular level using nuclear techniques

Objective To investigate the biological effects and the effecting mechanisms of rare earth elements La,Gd and Ce on cultured rat cells.Methods The biological effects of La 3+ on cultured rat cells and the subcellular distribution of La and Gd and Ce, and the inflow of 45Ca 2+ into the cells and total cellular calcium were measured by isotopic tracing, Proton Induced X Ray Emission Analysis (PIXE) and the techniques of biochemistry and cellular biology.Results La 3+ at the concentration of 10 -10(or 10 -9)～10 -6mol/L significantly increased quantity of incorporation of 3H-TdR into DNA, total cellular protein and the activity of succinic dehydrogenase of mitochondria. The cell cycle analysis showed that the proportions of cells in S phase were accordingly increased acted by La 3+ at above range of concentration. But these values were significantly decreased when concentration of La 3+ raised to 10 -4～10 -3mol/L. It was further discovered that La,Gd,and Ce distributed mostly in the nuclei, and then in membranes. Gd and Ce also promoted the inflow of 45Ca 2+ into the cells and increased the total calcium content in cells.Conclusions ① La 3+ at a wide concentration range of 10 -10( or 10 -9)～10 -6mol/L promotes proliferation of cultured rat cells, but at even higher concentration (10 -4～10 -3mol/L) shows cellular toxicity, and there is a striking dose-effect relationship. ② La,Gd and Ce can enter the cells and mainly distribute in the nuclei. ③ Gd and Ce can promote the inflow of extracellular Ca 2+ into the cells and increase total cellular calcium.