O'Hara M D, Xiong Q B, Boyer J W, Leeper D B
Department of Radiation Oncology and Nuclear Medicine, Thomas Jefferson University, Philadelphia, PA 19107-5097.
Int J Hyperthermia. 1992 Jul-Aug;8(4):451-61. doi: 10.3109/02656739209037983.
Thermal response, thermotolerance development and stepdown heating (SDH) in the murine bone marrow granulocyte-macrophage (CFU-GM) progenitors were determined in vitro. Marrow was removed from femora and tibia, heated in McCoy's 5A medium plus 15% FBS and cultured in soft agar in the presence of three different sources of colony stimulating factor. D0's (+/- SE) for survival curves of CFU-GM heated in vitro were 147 +/- 13, 71 +/- 9, 37 +/- 2, 19 +/- 0.7, 11 +/- 1, and 4.3 +/- 0.3 min, for temperatures of 41.8, 42, 42.3, 42.5, 43 and 44 degrees C, respectively. Arrhenius analysis showed inactivation enthalpies of 812 +/- 9 KJoules/mole (193 +/- 2 Kcal/mole) above, and 2142 +/- 157 KJoules/mole (509 +/- 37 Kcal/mole) below, an inflection at 42.5 degrees C. Thermotolerance development was evident during prolonged hyperthermia exposure at temperatures below 42.5 degrees C (chronic hyperthermia) as a change in the slope of the survival curves after approximately 110 min of heating. Thermotolerance development at 37 degrees C after exposure to temperatures of 43 degrees C or greater (acute hyperthermia) was assessed by fractionated heat treatments consisting of an initial heat treatment (15 min at 44 degrees C) followed by incubation at 37 degrees C and challenge with 15 min or 25 min at 44 degrees C. Maximum thermotolerance occurred after 210 and 330 min at 37 degrees C, respectively. The half-time for maximum thermotolerance development was 36 min. Depending on the amount of heat damage and the maximum amount of thermotolerance development, the decay of thermotolerance was complete after approximately 48-72 h at 37 degrees C. An exposure of 10 min at 44 degrees C before incubation at 40 or 41 degrees C (stepdown heating) reduced the slope of the 40 or 41 degrees C survival curves by inhibiting thermotolerance development that would have otherwise occurred. D0's were 100 +/- 19 and 45 +/- 5 min for 40 and 41 degrees C incubation preceded by 10 min at 44 degrees C, respectively. These studies indicate that whole-body or regional hyperthermia protocols designed either to treat solid tumours or to purge leukemic stem cells from marrow ex vivo should avoid inadvertent temperature elevations to large volumes of marrow. Although, marrow progenitors are capable of thermotolerance development during exposure to temperatures up to 42.3 degrees C, results suggest that conditions of stepdown heating may prevent thermotolerance development.
在体外测定了小鼠骨髓粒细胞-巨噬细胞（CFU-GM）祖细胞的热反应、耐热性发展和逐步降温加热（SDH）。从股骨和胫骨中取出骨髓，在含有15%胎牛血清的 McCoy's 5A 培养基中加热，并在三种不同来源的集落刺激因子存在下于软琼脂中培养。体外加热的 CFU-GM 存活曲线的 D0（±SE）在温度为 41.8、42、42.3、42.5、43 和 44℃时分别为 147±13、71±9、37±2、19±0.7、11±1 和 4.3±0.3 分钟。阿伦尼乌斯分析表明，在 42.5℃的拐点以上，失活焓为 812±9 千焦/摩尔（193±2 千卡/摩尔），以下为 2142±157 千焦/摩尔（509±37 千卡/摩尔）。在低于 42.5℃的温度下长时间热疗暴露（慢性热疗）期间，耐热性发展明显，表现为加热约 110 分钟后存活曲线斜率的变化。通过分级热处理评估在暴露于 43℃或更高温度（急性热疗）后在 37℃时的耐热性发展，分级热处理包括初始热处理（44℃下 15 分钟），然后在 37℃下孵育，并在 44℃下用 15 分钟或 25 分钟进行挑战。最大耐热性分别在 37℃下 210 分钟和 330 分钟后出现。最大耐热性发展的半衰期为 36 分钟。根据热损伤的程度和最大耐热性发展的程度，在 37℃下约 48 - 72 小时后耐热性完全衰减。在 40 或 41℃孵育前在 44℃暴露 10 分钟（逐步降温加热）通过抑制原本会发生的耐热性发展降低了 40 或 41℃存活曲线的斜率。在 44℃下 10 分钟后接着在 40 和 41℃孵育的 D0 分别为 100±19 和 45±5 分钟。这些研究表明，旨在治疗实体瘤或从体外骨髓中清除白血病干细胞的全身或局部热疗方案应避免大量骨髓意外升温。尽管骨髓祖细胞在暴露于高达 42.3℃的温度期间能够发展耐热性，但结果表明逐步降温加热的条件可能会阻止耐热性发展。
