TUNEL法检测大鼠死后心肌细胞核DNA断裂与死亡时间关系研究

A study on correlation between myocardial nuclear DNA fragmentation and postmortem interval by TUNEL in rats

目的用原位脱氧糖核苷酸末端转移酶介导的缺口末端标记法（TUNEL）观察大鼠死后心肌细胞DNA断裂与死亡时间（postmortem interval，PMI）的关系。方法建立SD大鼠死亡模型，在25.1℃，分别于死后6、12、24、36、48、60h提取大鼠心肌组织进行TUNEL检测，显微成像系统采集图像，经计算机图像系统分析及统计学处理。结果死后6—60h，心肌细胞核荧光染色依次由绿色、黄绿色亮度增强、亮黄色到荧光亮度减弱；形态由扁圆形或柱状，大小较均匀，到体积增大、呈毛虫状、多数核碎裂到形态不规整，大部分核形成碎片；心肌组织细胞核的IG，死后6h至36h依次增高，36h达到高峰，随后下降；心肌细胞核DNA的AG死后24h最高。结论死后各时间点，心肌细胞核的荧光颜色和亮度以及细胞核的大小和形态有一定的变化规律。

Objective To investigate correlation between myocardial nuclear DNA fragmentation and postmortem interval （PMI） by TUNEL in rats. Methods 18 healthy female Spregue-Dawley rats were excured by cervical dislocation and placed at environment temperature of 25.1℃ for 6h, 12h, 24h, 36h, 48h, and 60h, respectively. Myocardial tissues were sampled at each postmortem interval. Nuclear DNA fragmentation was detected by TUNEL assay. The images were captured and analyzed by MICRO-COSMOS computer image analysis system. The data were processed statistically. Results The myocardial nuclei were fluoresce-labeled from green, kelly, bright yellow to dim green. The shape of myocardial nuclei was oblate or column with relatively even size. Thereafter, myocardial nuclei were changed to palmer in shape with enlargement in size, most of which were karyorrhexized with extenson of postmortem interval from 6 to 60h. The IG （ integral grey） of myocardial nuclei was increased from 6h to 36h after death and decreased thereafter, which peaked at 36h. The AG （ average grey） of myocardial nulei peaked at PMI 24h. Conclusion It is found that the fluorescent color and brightness of the nuclei, the size and morphology of the nuclei were changed time-dependently after death, suggestig that there is a correlation between myocardial nuclear DNA fragmentation and postmortem interval.