"Study of early radiation-induced cell death using two cell lines with different radiosensitivities in vitro"

采用放射敏感型大鼠卵黄囊肿瘤细胞株NMT-1和放射耐药变异细胞株NMT-1R，研究其放射敏感性、化学敏感性和热敏性的差异。NMT-1R的辐射灵敏度Do为165 cGy，是NMT-1的1.7倍。NMT-1R的外推数n为1.48，而NMT-1的外推数为1.8.2。虽然两种细胞系在2 Gy剂量照射后都观察到明显的G2延迟，但NMT-1R从G2阻滞中恢复的时间比NMT-1短。在NMT-1.3中观察到G1骤停。3 .与NMT-1R细胞相比，NMT-1细胞在5 Gy以上辐照后表现出更高的早期形态学改变，尤其是凋亡的发生率。5gy辐照后24 h内观察NMT-1细胞凋亡的发展与时间的关系。单剂量5gy时，细胞凋亡发生率达到平稳期。NMT-1对顺铂的敏感性是NMT-1R的4倍（基于ID_<50 bb0.6）。顺铂对两种细胞系的协同效应为1.30-1.39倍，与时间进程和序列无关，6 h内联合放疗对两种细胞系均有协同效应。在42ºC温度下，NMT-1的热敏感TO为2.5 h，而NMT-1R的热敏感TO为0.7 h， NMT-1R比NMT-1.8更敏感。NMT-1和NMT-1R在间隔6 h时的热容比分别为8.09和6.28。加热后主要诱导NMT-1细胞表达HSP70。

A radiosensitive rat yolk sac tumor cell line, NMT-1, and A radioresistant variant cell line, NMT-1R were used in this study to investigate the difference of radiosensitivity, chemosensitivity and thermosensitivity.1.For NMT-1R,Do for radiation sensitivity was 165 cGy, 1.7 times as large as for NMT-1. The extrapolation number, n, was 1.48 for NMT-1R although that for NMT-1 was 1.8.2.Although a clear G2 delay was observed after irradiation with a dose of 2 Gy for both cell lines, NMT-1R had a shoreter recovery time from G2 block than NMT-1. G1 arrest was observed in NMT-1.3.NMT-1 showed much higher incidence of early morphological changes, especially apoptosis, after irradiation with more than 5 Gy compared with NMT-1R cell.4.Development of apoptosis in NMT-1 was observed as a function of time within 24 h after irradiation with a dose of 5 Gy. The incidence of apoptosis reached a plateau with a single dose of 5 Gy.5.NMT-1 was 4 times as sensitive to cisplatin as NMT-1R based on ID_<50>.6.Cisplatin had a synergistic effect by a factor of 1.30-1.39, which was independent of the time-course and sequence in combination with radiation within 6 h on both cell lines.7.The "TO" for heat sensitivity was 2.5 h at temperature of 42 ﾟC for NMT-1 but that for NMT-1R was 0.7 h. NMT-1R was more sensitive to heat than NMT-1.8.Thermal tolerance ratios for NMT-1 and NMT-1R at 6 hr interval was 8.09 and 6.28 respectively. HSP70 expression was induced predominatly on NMT-1 cells following heating.