Abstract: BACKGROUND ＆ AIM： To study the effect of holmium ions on DNA breakage of mice liver cells and the effect of holmium element on apoptosis of zoic cells in vivo. MATERIAL AND METHODS: Group 1: Mice were administered orally with daily dose of 50 mg/kg of holmium chloride solution for 5 days；Group 2～3: Mice were treated intraperitoneally with daily dose of 60 mg/kg and 120 mg/kg of holmium chloride solution twice respec tively. Group 4: Mice were treated intraperitoneally with a single dose of 320 mg/kg of holmium chloride solution. In group 1～3, the interval of poisoning was 24 h, and DNA was extracted from mice livers 24 h after the last poisoning in groups above. Group 5: Mice were administered intraperitoneally with the same volume of saline as below. Group 6～9: Mice were treated intraperitoneally with a single dose of 80 mg/kg of holmium chloride solution and DNA was extracted at 12, 24, 48 and 96 h respectively. Agarose gel electrophoresis was performed to observe the tapes'change. RESULTS: In group 7, a continual diffusive tailed tape was showed, but no obvious DNA-tailed tape observed in all the other groups. Meanwhile, no DNA ladder was found, too. CONCLUSIONS: It is possible that the extension of DNA breakage caused by holmium ions to mice liver cells was associated with dose, treating duration and DNA-repair, which had no specificity. The results suggest that holmium element couldn't induce apoptosis of mice liver cells in vivo in the experiments.

Key words: holmium element, DNA breakage, DNA ladder, DNA repair, apoptosis.