Hyperthermic killing and hyperthermic radiosensitization in Chinese hamster ovary cells

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1981

OSTI ID:5742645

Holahan, E V

G/sub 1/ and asynchronous Chinese hamster ovary cells were heated and/or x-irradiated in medium at pH 7.4 or 6.75. When asynchronous cells were x-irradiated (13 Gy) at either pH and then incubated at pH 6.7, cell survival was enhanced 2 to 3 fold because of either increased recovery from radiation damage or decreased fixation of damage. In contrast, thermal sensitivity increased at pH 6.75 as expressed by a decrease in the shoulder and an increase in the slope of the heat survival curves. Thermotolerance developed after 200 to 300 min of heating, although the survival was significantly greater at pH 7.4 than at pH 6.7. When cells were heated before irradiation at 37/sup 0/C, the shoulder of the heat-plus-radiation survival curves decreased and the slope increased with increased heat killing independent of temperature or extracellular pH. However, when thermotolerance was induced with continuous or fractionated heating, the slopes of the heat-plus-radiation survival curves decreased until they were parallel to the radiation only survival curve suggesting tolerance to hyperthermic radiosensitization. Because of the increased thermal sensitivity of cells in acidic medium, more heat killing and greater heat radiosensitization were induced in cells treated at pH 6.75 than 7.4. The Thermal Gain Factor (an in vitro equivalent to the Therapeutic Gain Factor) increased with increased heating. The effect of cold storage (O/sup 0/ to 4/sup 0/C, 3 h) on heat killing and heat radiosensitization was examined in G/sub 1/ and S phase cells after mitotic selection. Cold storage delayed progression into G/sub 1/ (20 to 60 min) and S (90 to 120 min), and also increased the thermal sensitivity by 2 to 3 fold.

• Research Organization: Colorado State Univ., Fort Collins (USA)
• OSTI ID: 5742645
• Country of Publication: United States
• Language: English

Related Subjects

560121* -- Radiation Effects on Cells-- External Source-- (-1987)
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ANIMALS
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
BODY TEMPERATURE
CELL CULTURES
CELL KILLING
ELECTROMAGNETIC RADIATION
HAMSTERS
HYPERTHERMIA
IONIZING RADIATIONS
MAMMALS
PH VALUE
RADIATION EFFECTS
RADIATIONS
RADIOSENSITIVITY
RADIOSENSITIVITY EFFECTS
RODENTS
SURVIVAL CURVES
VERTEBRATES
X RADIATION