the effect of gamma-irradiation dose and post-irradiation incubation time on apoptosis induction in human breast carcinoma cells

introduction: different environmental factors such as drugs, ionizing radiation, etc can induce apoptosis.in the present study the effects of dose- rate and post-irradiation incubation time on gamma radiation inducedapoptosis in human breast carcinoma cell line (t-47d) (invasive ductal carcinoma) was investigated. material and methods: the t-47d cells were cultured in t25 flasks and during log phase of growth,the cells were counted and exposed to 4,8,12 and 16gy gamma radiation. untreated and etoposide treated cellsserved as negative and positive controls, respectively. at 24,48 and 72 hours post irradiation, the cells wereharvested and stained with ho/pi and ao/pi for morphological and flow cytometric analysis, respectively.absolute and relative numbers of live(l), apoptotic (ap) and dead (d) cells were determined using the abovementioned methods and reported as mean í sd. results: in comparison to normal controls, gamma radiation inhibited growth of t-47d cells in a dose andpost-irradiation incubation time dependent manner which was defined by reduction of cell proliferation justafter exposure that continued for 48 hours and was followed by cell count reduction. the relation betweenirradiation dose and apoptosis induction was not linear and inverted at 8gy after 48 hours post irradiation.therefore, maximum apoptotic response (%) occured during 48 hours after expossure to 8gy. however,relative numbers of a live and dead cells decreased and increased respectively in a dose and time dependentmanner. conclusions: the present study revealed that gamma-irradiation could induce apoptosis in t-47d cellline and the rate of apoptosis was radiation dose dependent but this relation was not linear and in higherdoses became inverted . however, cell viability and death were dose and time dependent.