Abstract: BACKGROUND ＆ AIM: To study the DNA damage of BALB/c mice caused by multiple treatment with low－dose methotrexate (MTX)and the protective effect of folinic acid(FA). MATERIAL AND METHODS:After ip MTX at dose of 0.5 mg/kg once a week for 8 weeks, DNA damage of peripheral lymphocytes and bone marrow cells were examined by single cell gel electrophoresis(SCGE). RESULTS: There were signifi cant differences of the tail length and the frequency of tailing cells between MTX and the control. However, there were no signifi cant differences between MTX＋FA and the control. CONCLUSION: SCGE is a rapid, simple and sensitive technique for detecting DNA damage caused by low dose methotrexate and folinic acid could protect peripheral lymphocytes and bone marrow cells DNA from damage induced by MTX.

Key words: methotrexate, folinic acid, single cell gel electrophoresis(SCGE), DNA damage