METHODS: SD rats were randomly divided into four groups: normal control group(NC), normal fluctuation group(NF), diabetes group(DM)and diabetes fluctuation group(DF). Diabetic models were established through intraperitoneal injection of STZ. A certain amount of glucose was injected in the rats of group NF and DF in an intraperitoneal mode three times a day after the model was established, thereby causing blood glucose fluctuations. Rats were killed and the retinal tissues were taken in the 8th week. Single cell gel electrophoresis(SCGE)technique was adopted for detecting DNA injury extent in the retina tissue.

RESULTS:Groups NF and DF showed significant and regular fluctuations. The curve of blood glucose fluctuations was relatively stable. All values of MBG, SDBG, LAGE and M were significantly increased compared with group NC. Group DF was increased more significantly. It was statistically significant(P<0.01). SCGE showed that there were DNA damages in different levels in the cells of group NF, DM and DF. Indicators of cells such as TL, TDNA%, TM, OTM were higher than that in group NC. It was statistically significant(P<0.01). The comparison difference between two groups was also significant(P<0.01).

CONCLUSION: Rat retinal tissues have DNA injury during early diabetic period. DNA injury is gradually aggravated with blood glucose fluctuation. It indicates that high blood glucose and blood glucose fluctuation are involved in the mechanism of cell DNA injury, and they may be one of DR early event, have played a certain role in the incidence of DR.