RNA Degradation And Estimation Of Postmortem Interval In Rat Brain-a Pilot Study

Objective: To study the ratio of GAPDH mRNA/18s rRNA after different postmortem intervaland investigate the application for estimating the time of postmortem interval in forensic medicineaspect.Methods: SD Rats were killed at 0d, 1d, 2d, 3d, 5d, 7d after respectively postmortem intervalby CO₂ asphyxia. TRIzol Reagent was used to isolate total RNA from SD rate's cerebral. The ratioof GAPDH mRNA/18s rRNA was detected by RT-PCR technology and gel image analysistechnology. The results were assessed by statistic analysis.Results (1) In our study, the degradation of GAPDH mRNA in the cerebral scarely was detectedup to 2d, but the content of GAPDH mRNA decreased markedly in the following 3d 5d 7d. Thecontent of 18s rRNA hardly changed along with postmortem interval. (2) The temperature affectdthe degradation of GAPDH mRNA (the higher of temperature, the more rapid of decay), but it hadless influence on 18s rRNA. (3) The correlation between ratio(Y) of GAPDH mRNA/18s rRNA inthe cerebral and postmortem interval(X) were calculated by statistic analysis: At 20℃, Y=0.62—0.004X (R=-0.981, P<0.001) ;At 15℃, Y=0.965-0.001X (R=-0.709, P<0.001) .Thecorrelation of postmortem interval and ratio of GAPDH mRNA/18s rRNA was significant instatistics.Conclusion: The rate of GAPDH mRNA decay at 20℃ was more rapid than the rate at 15℃along with postmortem interval. But the rate of 18s rRNA degradation was hardly affected bydifferent temperature. The ratio of GAPDH mRNA and 18s rRNA in the cerebral is a useful targetfor estimating the time of postmortem interval.