Radiation induced Delayed Effect in Human Normal Liver HL-7702 Cells

Key words: 
• delayed effect /
• micronucleus /
• apoptosis /
• cell damage /
• genomic instability

Abstract: Human normal liver cell line HL-7702 cells were irradiated with different doses of Xrays. Micronucleus and apoptosis rates in the irradiated cells were measured with cytokinesisblock micronucleus method and Annexin VFITC apoptosis detection kit， respectively. Experimental data showed that the micronucleus and apoptosis rates increased obviously with increasing irradiation dose. After seven population doublings， the micronucleus and apoptosis rates of the cells surviving exposure to the Xrays reduced to the same levels as nonirradiated control cells; the progenies of the cells were secondly exposed to Xrays at the same dose of 2.5 Gy. We found that the progenies of the cells surviving the first irradiations of the various doses showed markedly differential micronucleus frequencies and apoptotic rates. Although the same dose of 2.5 Gy was applied in the second irradiations， the micronucleus frequencies and apoptotic rates of the progenies of the cells initially exposed at higher doses were significantly higher than the others. These results indicate that Xrays lead to genomic instability in HL7702 cells， which is an important manifestation of radiationinduced delayed effect， and a second radiation stimulus makes the delayed effect in the progeny of the previously irradiated cells be expressed obviously.
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