A quantitative study of radiation-induced apoptosis in two rat yolk sac tumour cell lines with different radiosensitivities in vitro

Abstract

Two rat yolk sac tumour cell lines with different radiosensitivities were used to quantify the extent of apoptosis following irradiation by using a DNA fragmentation assay in vitro. Apoptosis was also confirmed by fluorescence analysis of nuclear morphological changes by using Hoechst 33258. A radiosensitive cell line, NMT-1 cells, showed morphological changes characteristic of apoptosis by fluorescence microscopic observation at 24 hours after irradiation with a single dose of 10 Gy. Development of apoptosis in NMT-1 cells was observed as a function of time within 24 hours after irradiation. There was a significant increase in the amount of apoptosis between 2 and 5 Gy only in NMT-1 cells but increasing the radiation dose from 5 Gy to 10 Gy did not result in increased apoptosis. A radioresistant NMT-1R cells, on the other hand, displayed a small apoptotic response to an irradiation dose of 10 Gy at 24 hours after irradiation.