Ludwikow G, Ludwikow F, Johanson K J
Department of Radioecology, Swedish University of Agricultural Sciences, Uppsala.
Int J Radiat Biol. 1992 May;61(5):639-53. doi: 10.1080/09553009214551451.
Two cell lines, CHO and GC, different in their tissue origin, were investigated with the aim of discovering the correlation between the level of 125I-T3 binding and chromosomal damage induced by 125I decay. Incubation of cells with 125I-T3 has been performed in two exposure schedules: continuous incubation for one to six cell cycles and a pulse-chase schedule involving exposure for one cell cycle. The cellular uptake of 125I-T3, its compartmentization and kinetics were different in the two cell lines. GC cells contained about 7 times more 125I-T3 than CHO cells when incubated with the same external 125I activity concentration (74 kBq of 125I-T3 ml-1 medium). Approximately 70% of the cellular 125I-T3 was found in nuclei of GC cells and only 5% in the nuclei of CHO cells. During the long-term incubation of GC cells with 74 kBq of 125I-T3 ml-1 medium, the 125I activity concentration in cells and their nuclei initially decreased by a half, and thereafter reached a plateau after the third doubling time. In CHO cells and nuclei a very slow linear increase of 125I activity was observed. In GC cells, micronucleus frequency was found to be correlated with nuclear 125I activity. One cell cycle pulse labelling with 74 kBq of 125I-T3 ml-1 medium caused a significant enhancement of micronucleus frequency above the control level during six doubling times, with a maximum at the first post-labelling doubling time. In GC cells continuously incubated with 74 kBq of 125I-T3 ml-1 medium, the micronucleus frequency increased with the incubation time. A model of T3 receptor-dependent dose delivery to nuclei of GC cells continuously incubated with 125I-T3 is proposed. The frequency of micronuclei in the CHO cell line continuously incubated with 125I-T3 did not differ significantly from the control, whereas in the pulse-chase schedule the mean frequency of micronucleated binuclear cells was lower during 4 post-labelling doubling times (significantly at the first and second post-labelling doubling time and insignificantly at the later doubling times) than in the control. Incubation of GC cells with various activity concentrations in medium for four cell cycles resulted in a linear increase of 125I activity in cells and nuclei; however, with a saturation in the region of highest 125I-T3 concentrations used. The frequency of binuclear cells bearing micronuclei was linearly dependent on the nuclear 125I-T3 concentration.
研究了两种组织来源不同的细胞系，即CHO和GC，目的是发现125I-T3结合水平与125I衰变诱导的染色体损伤之间的相关性。用125I-T3孵育细胞采用了两种暴露方案：连续孵育一至六个细胞周期和一种脉冲追踪方案，即暴露一个细胞周期。两种细胞系中125I-T3的细胞摄取、区室化和动力学有所不同。当用相同的外部125I活性浓度（74 kBq的125I-T3/ml培养基）孵育时，GC细胞所含的125I-T3比CHO细胞多约7倍。在GC细胞中，约70%的细胞内125I-T3存在于细胞核中，而在CHO细胞的细胞核中仅为5%。在用74 kBq的125I-T3/ml培养基对GC细胞进行长期孵育期间，细胞及其细胞核中的125I活性浓度最初下降一半，此后在第三个倍增时间后达到平稳期。在CHO细胞及其细胞核中，观察到125I活性呈非常缓慢的线性增加。在GC细胞中，发现微核频率与细胞核125I活性相关。用74 kBq的125I-T3/ml培养基进行一个细胞周期的脉冲标记，在六个倍增时间内导致微核频率显著高于对照水平，在标记后的第一个倍增时间达到最大值。在用74 kBq的125I-T3/ml培养基连续孵育的GC细胞中，微核频率随孵育时间增加。提出了一个T3受体依赖性剂量传递至与125I-T3连续孵育的GC细胞核的模型。与125I-T3连续孵育的CHO细胞系中的微核频率与对照无显著差异，而在脉冲追踪方案中，双核微核细胞的平均频率在标记后的4个倍增时间内（在标记后的第一个和第二个倍增时间显著，在随后的倍增时间不显著）低于对照。用培养基中不同活性浓度孵育GC细胞四个细胞周期，导致细胞及其细胞核中的125I活性呈线性增加；然而，在所用的最高125I-T3浓度区域出现饱和。带有微核的双核细胞频率与细胞核125I-T3浓度呈线性相关。
