PRODUCTION OF THYMINE BASE DAMAGE IN ULTRASOUND-EXPOSED EMT6 MOUSE MAMMARY SARCOMA-CELLS
PRODUCTION OF THYMINE BASE DAMAGE IN ULTRASOUND-EXPOSED EMT6 MOUSE MAMMARY SARCOMA-CELLS
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DOI：
10.2307/3576190
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发表时间：
1984-01-01
影响因子：
3.4
通讯作者：
MILLER, MW
中科院分区：
文献类型：
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作者：
DOOLEY, DA;SACKS, PG;MILLER, MW
小鼠乳腺肉瘤细胞系EMT6/Ro在0.5~30W/cm2(空间峰值)的强度范围内照射1min~1 MHz的连续波。通过碱降解试验确定了5，6-二羟基二氢胸腺嘧啶碱基损伤(TBD)产物的存在。产生的损害最大(.apprx.2.7次。10-3%t‘/T)，在10W/cm2的强度下，在这个强度上下迅速下降。10W/cm2超声波产生的基面损伤量大约相当于12krad的伽马射线吸收剂量所产生的损伤量。10W/cm2超声波作用后即刻的细胞检测结果显示。14%的细胞被裂解。然而，测试表明，是完整细胞的DNA维持了所有的待定疾病。存活数据表明，剩余的未裂解细胞群体.apprx。5%的细胞存活，而暴露于12krad的细胞则没有存活。此外，细胞以5W/cm2的功率暴露长达5min。随着暴露时间的增加，TBD呈增加趋势，因此在5分钟时的产生率为.apprx。比1分钟暴露时间大3倍。当细胞在4bar的静水压力下以10W/cm2的功率超声作用2min时，TBD被完全抑制。加入自由基清除剂β-MEA[硫醇]和半胱胺可消除慢性阻塞性肺疾病，但对存活率影响很小。压力和清除剂实验证明，TBD是由空化诱导的自由基引起的。根据这些自由基的半衰期和扩散距离的值，结果表明，至少部分气泡坍塌发生在细胞内。
Mouse mammary sarcoma cells, line EMT6/Ro, were exposed for 1 min to 1 MHz continuous wave ultrasound over a range of intensities from 0.5 to 30 W/cm2 (spatial peak). The presence of thymine base damage (TBD) products of the 5,6-dihydroxydihydrothymine type was determined by an alkali degradation assay. Production of damage was greatest (.apprx. 2.7 .times. 10-3% t''/T) at an intensity of 10 W/cm2 and fell off rapidly above and below this intensity. The amount of base damage produced at 10 W/cm2 ultrasound was approximately equivalent to the damage produced by a .gamma.-ray absorbed dose of 12 krad. Assay of cells immediately after sonication at 10 W/cm2 showed that .apprx. 14% of the cells were lysed. Tests showed that it was the DNA of the intact cells, however, which sustained all of the TBD. Survival data demonstrated that of the remaining unlyzed cell population .apprx. 5% were viable, whereas cells exposed to 12 krad showed no survival. Additionally, cells were exposed for up to 5 min at 5 W/cm2. An increase in TBD was demonstrated with increasing time of exposure such that the rate of production at 5 min was .apprx. 3 times greater than that of a 1-min exposure. TBD was found to be completely suppressed when cells were sonicated at 10 W/cm2 for 2 min under 4 bar of hydrostatic pressure. Addition of the radical scavengers .beta.-MEA [mercaptamine] and cystamine eliminated TBD but had minimal effect on survival. The pressure and scavenger experiments demonstrate that TBD results from cavitation-induced free radicals. Based on the values for both the half-life and diffusion distance of such radicals, the results indicate that at least part of the bubble collapse occurs intracellularly.