Action of caffeine on x-irradiated HeLa cells. III. enhancement of x-ray-induced killing during G/sub 2/ arrest
- Washington Univ. School of Medicine, St. Louis, MO
The ability of caffeine to enhance the expression of potentially lethal x-ray damage in HeLa S3 cells was examined as a function of the age of the cells in the generation cycle. Synchronous populations were irradiated at different times after mitotic collection and treated for various intervals with 1 mM caffeiene, which causes negligible killing of unirradiated cells. The response was thereby determined as a function of cell age at both the time of irradiation and the time of exposure to caffeine. The amount of cell killing depends strongly on when in the cycle caffeine is present and only weakly on when the cells are irradiated. If cells are irradiated in early G/sub 1/, caffeine treatment enhances killing for 2 to 3 hr. No additional enhancement is observed until 16 to 17 hr postcollection, corresponding to G/sub 2/; here they enter a second period of much greater sensitivity. Similarly, fluorodeoxyuridine resynchronized cells irradiated during S and treated with caffeine suffer no enhanced killing until they pass into this sensitive phase in G/sub 2/, approximately 7 hr after release from the fluorodeoxyuridine block. The sensitive period appears to coincide with G/sub 2/ arrest. The rate and extent of killing during this period are dependent upon the x-ray dose and the caffeine concentration. In the absence of caffeine, cells irradiated in G/sub 1/ lose sensitivity to caffeine in about 9 hr; they do so faster in G/sub 2/. It is concluded that the potentially lethal x-ray damage expressed on treatment with caffeine is retained for many hours in the presence of caffeine and is maximally manifested by G/sub 2/-arrested cells.
- OSTI ID:
- 6433323
- Journal Information:
- Radiat. Res.; (United States), Journal Name: Radiat. Res.; (United States) Vol. 76:2; ISSN RAREA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AGE DEPENDENCE
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
CAFFEINE
CELL CULTURES
CELL CYCLE
CELL KILLING
DOSE-RESPONSE RELATIONSHIPS
DRUGS
ELECTROMAGNETIC RADIATION
HELA CELLS
HETEROCYCLIC COMPOUNDS
IN VITRO
IONIZING RADIATIONS
IRRADIATION
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PURINES
RADIATION EFFECTS
RADIATIONS
RADIOSENSITIVITY EFFECTS
SENSITIVITY
SYNCHRONOUS CULTURES
X RADIATION
XANTHINES