Abstract: Objective To observe the changes of relative expression of myocardial various RNAs in rats died of different causes and their relationship with PMI. Methods The rat models were established in which the rats were sacrificed by broken neck, asphyxia, and hemorrhagic shock. Total RNAs were extracted from myocardium. The quantitative real time PCR was used to calculate threshold cycle values of RNAs including glyceraldehyde-3-phosphate dehydrogenase （GAPDH）, β-actin, inducible nitric oxide synthase （iNOS）, hypoxia-inducible factor-1 （HIF-1）, tumor necrosis factor-α （TNF-α）, interleukin-6 （IL-6）, and U6 small nuclear RNA （U6 snRNA） and to study the changes of the relative expressions of various indexes with PMI. Results U6 snRNA with stable expression level could be used as appropriate internal control. In the early PMI, the relative expression of GAPDH, HIF-1, iNOS, TNF-α, and IL-6 more characteristically increased in groups of asphyxia and hemorrhagic shock than in group of broken neck, but the quantity of β-actin decreased in all groups. In the late PMI, all the relative expressions significantly declined in correlation with the degradation of RNA. Conclusion The characteristic changes of each RNA expression can be used as references to estimate PMI in deaths by different causes.

Key words: forensic pathology, myocardium, RNA, postmortem interval, rats