Abstract
Germanium is a transition metal commonly used in the electronics industry. It has been reported that germanium could cause neuropathy, nephropathy and myopathy in the experimental animals. However, the studies on the cellular and molecular effect of germanium are quite limited. Previous study indicated that germanium oxide（GeO2）induced G1 and G2 arrest in the CHO K1 cells. A serious of studies were thus conducted to investigate the appropriate condition for the usage of GeO2 as a chemical to synchronize cell at a particular stage. The CHO K1 cells were initially treated with 5mM GeO2 for 12 hours, and fresh medium was replaced. After 12~15 hours, the cells were synchronized at G1 phase. However, the level of cdc2 phosphorylated at the 15th amino acid cdc2( 15Tyr-P) was discordance with the cell distribution. The cells was then treated with 5mM GeO2 for 15 or 18 hours and accumulated most of the cells at G2 stage. After release for 9 or 12 hours, the cells were markedly synchronized at G1 phase. However, estimation of mitotic index showed that the cells did not move into M phase at a similar rate. Alternatively, we treated the cells with 22mM GeO2 for 48 hours to arrest them at G2 phase. The cells progressed in the cell cycle in a synchronized manner after changing to fresh medium, and cells stayed were predominantly in the G1 phase when released for 21 hours. The cyclin A and cdc2（15Tyr-P）expression were correlated to the population of cells at specific stages. The results implied that exposure of cells to 22mM GeO2 for 48 hours in a feasible method to synchronize cells at G2 stage