Abstract: Objective To observe the degradation of actin in cardiac muscle, liver, spleen, lung, kidney, brain and skeletal muscle of rats after death and to find an objective parameter for the late postmortem interval (PMI) estimation. Methods Twenty eight clear Sprague Dawley rats were killed by suffocating and put into an artificial climate incubator (set at 20 ℃) for 0, 24, 48, 72, 96, 120 and 168 h, respectively. The actin contents in the above tissues were quantitated by Western- blot assay and collected by Image- Pro Plus 5.0 image analysis system, and were then statistically analyzed with the SPSS11.5 software. Results Actin content in all these tissues decreased gradually with prolonged PMI. The degradation differences between the groups was statistically significant (P<0.05), with the degradation in the brain fastest, then the lung, the spleen, the liver, the kidney, the cardiac muscle and the skeletal muscle in order. There was a strong correlation between actin degradation and PMI, and the coefficient of determination (R2) exceeded 0.75 in all these tissues. Conclusion Although with tissue disparity in degradation, the actin contents in cardiac muscle, liver, spleen, lung, kindey, brain and skeletal muscle of rats decreased gradually with prolonged PMI, which may potentially be a useful parameter for the late PMI estimation.

Key words: forensic pathology, postmortem interval, actin, western-blot