中文摘要：

目的：研究低频低强度超声波诱导白血病细胞株K562凋亡的作用及其机制.方法：取对数生长期的K562细胞,分成实验组和对照组,用MTT法计算细胞存活率,流式细胞仪判断细胞凋亡,瑞氏染色和透射电镜观察细胞照射后有无出现凋亡,分光光度法检测照射前后K562细胞Caspase-3的活性改变.结果：超声照射各组间细胞存活率与对照组相比有统计学差异,但组间无差异;瑞氏染色光镜下可见0.03 W组和0.10 W组细胞出现细胞核固缩等早期凋亡的改变,0.25 W组出现凋亡小体等典型凋亡改变;流式细胞仪检测0.25 W组凋亡率为38.87%;照射前后K562细胞Caspase-3的活性无差异.结论：低频低强度超声波对白血病细胞株K562有诱导凋亡作用,与照射强度和时间无明显相关.低频低强度超声波诱导K562的凋亡可能不通过Caspase-3的途径.

英文摘要：

Objective To investigate the effect of low frequency and low intensity K562 and to clarify the role of Caspase-3 in the effect. Methods K562 cells in log ultrasound on leukemia cell lines phase were divided into control group and experimental group. The intensity of low frequency（20 kHz） and low intensity ultrasound were 0.03, 0.10 and 0.25 W · cm^ -2 respectively. The exposure time were 30 and 60 s respectively. K562 cells were incubated in 24-well culture plates for different time of periods （6,24,48 h） after sonication and the number of vital cells was tested by MTT assay. The morphology of apoptosis was analyzed by Wright＇ s stain and transmission electron microscopy. The percentage of apoptosis were studied by flow cytometry （FCM）. The activation of Caspase-3 was tested by Caspase-3 kit with spectrophotometric method. Results The absorbance value of MTT decreased significantly after exposure. The highest apoptosis was found in 0.25 W group after 30 s sonication and 6 h incubation. Morphological alterations observed in cells after exposure to ultrasound included： cell shrinkage, membrane blebbing, chromatin condensation, nuclear fragmentation, and apoptotic body formation. FCM revealed that the percentage of apoptosis of ceils in control group, in 0.03 W group, in 0.10 W group and in 0.25 W group was 7.60% ,35.95%, 11.57% and 38.87% respectively. There were no significant difference of activation of Caspase-3 between control and experimental group（0.25 W group after 30 s sonication and 6 h incubation）. Conclusion Low frequenchy and low intensity ultrasound can induce apoptosis in K562 cell lines after the exposure. The effect is not relevant to the intensity and exposure time of ultrasound.