大鼠死后不同组织电导率与死亡时间关系的研究

目的测定不同死亡时间大鼠脑、肺、肝和骨骼肌电导率,研究不同组织器官EC与PMI的关系。方法 SD大鼠处死后,保存于25℃恒温条件下,于死后即刻(0d)、1d、2d、3d、4d、5d、6d和7d提取大鼠脑、肺、肝和骨骼肌,四种组织器官与去离子水按照一定比例制成浸渍液,测定各组织器官浸渍液EC值;分析其EC值与PMI的关系,建立与PMI关系的回归方程;比较大鼠死后四种组织器官EC变化规律,探讨不同组织器官腐败进程。结果死后1d内骨骼肌与脑组织EC无显著变化,2~7d快速增加;而肝、肺EC值在1d内已开始增加,且2~7d内均快速上涨。四种组织器官EC与PMI的关系用三次方程拟合较好,其中肝的相关系数最高,R~2=0.96,且四种组织器官的EC值在不同的PMI区段之间呈现出不同的增长规律。结论大鼠脑、肺、肝和骨骼肌EC与PMI相关性均较好,测定尸体组织器官EC有望成为法医实践中PMI推断的有效方法。

Study on the relationship between postmortem interval and electrical conductivity of different tissues

Objective To determine the electrical conductivity of cerebrum, liver, lung and muscle of rats at different postmortem intervals for investigating the relationship between EC and PMI. Methods Healthy Sprague-Dawley rats were sacrificed and kept at constant temperature of 25°C. Cerebrum, lung, liver and muscle were extracted at different PMIs of immediate (0d), 1d, 2d, 3d, 4d, 5d, 6d and 7d, and their extraction liquids were prepared with ultrapure water at the ratio of 1g:10mL. EC were separately determined for different tissues and organs. The relationships between EC of different tissues and organs and PMI were analyzed and their regression functions were established. The characteristics of EC values for four tissues and organs were compared and their decomposition processes were discussed. Results EC of brain and muscle showed no significant changes within 1d, and increased rapidly during 2~7d; but EC of liver and lung started to increase within 1d and increased rapidly during 2~7d.The relationship between EC of different tissues and organs and PMI were well fitted with cubic equations and liver gained the highest coefficient (R2=0.96). Additional, the EC of four organs presented various increasing laws in different periods of PMI. Conclusion The EC of cerebrum, lung, liver and muscle of rats were well fitted with PMI and the determination of EC of cadaver tissues can be expected to become an effective method for PMI estimation in forensic practice.