Abstract: Objective To study the changes of DNA degradation in cells of rats and its relationship with the postmortem interval. Method 8 parameters of cell nuclear(including the tail length, the head radius, the percentage of head DNA,the percentage of tail DNA, the tail moment, the olive moment, the head area and the tail area) were chosen to study their changes in the procedure of DNA degradation in myocardium cells in 111 rats at different postmortem interval from 0 to 72 h by using single-cell gel electrophoresis(SCGE)technology and fluorescent microscope combined with auto-analysis-image system method. Results An evident comet tailing was observed in DNA of myocardium cells after electrophoresis, and their changes in all these 8 parameters of cell nuclear were greatly associated with the extension of postmortem interval,which indicate the degradation rate and degree of DNA in the nuclear has a close relationship with postmortem interval in the periods from 0 to 72 h in rats and significant difference were found with those groups (P<0.001). Conclusion The equations, which were concluded from our study, indicate the close relationship of degradation rate and degree of DNA in the nuclear with postmortem interval from 0 to 72 h, and provide an objective and exact new way to estimate the postmortem interval.

Key words: Single cell gel electrophoresis, Postmortem interval, DNA degradation, image analysis