Hyperthermic killing and hyperthermic radiosensitization in Chinese hamster ovary cells: effects of pH and thermal tolerance

Journal Article · Sun Jan 01 00:00:00 EST 1984 · Radiat. Res.; (United States)

DOI:https://doi.org/10.2307/3576193· OSTI ID:5301098

Holahan, E V ^[1]; Highfield, D P; Holahan, P K; Dewey, W C

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1. Department of Experimental Hematology, Bethesda, MD

To quantitatively relate heat killing and heat radiosensitization, asynchronous or G/sub 1/ Chinese hamster ovary (CHO) at pH 7.1 or 6.75 were heated and/or X-irradiated 10 min. later. Since no progression of G/sub 1/cells into S phase occurred during the heat and radiation treatments, cell cycle artifacts were minimized. Hyperthermic radiosensitizaiton was expressed as the thermal enhancement factor (TEF), defined as the ratio of the D/sub 0/ of the radiation survival curve to that of the D/sub 0/ radiation survival curve for heat plus radiation. The TEF increased continuously with increased of the heat killing at 45.5/sup 0/ C, and for a given amount of heat killing, the amount of heat radiosensitization was the same for both pH's. When cells were heated chronically at 42.4/sup 0/ C at pH 7.4, the TEF increased initially to 2.0-2.5 and then returned to near 1.0 during continued heating as thermal tolerance developed for both heat killing and heat radiosensitization. However, the shoulder (D/sub q/) of the radiation survival curve for heat plus radiation did not manifest thermal tolerance. These results suggest that heat killing and heat radiosensitization have a target(s) in common (TEF results), along with either a different target(s) or a difference in the manifestation of heat damage (D/sub q/ results). Since low pH reduced the rate of development of thermal tolerance during heating at low temperatures, low pH enhanced heat killing more at 42-42.5/sup 0/ C than at 45.5 C where thermal tolerance did not develop. These findings agree with animal experiments suggesting that in the clinic, a therapeutic gain for tumor cells at low pH may be greater for temperatures of 42-42.5/sup 0/ C than of 45.5/sup 0/ C.

• OSTI ID: 5301098
• Journal Information: Radiat. Res.; (United States), Vol. 97:1
• Country of Publication: United States
• Language: English

Related Subjects

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
CELL KILLING
RADIOINDUCTION
FIBROBLASTS
BIOLOGICAL RADIATION EFFECTS
HYPERTHERMIA
RADIOSENSITIVITY EFFECTS
EXPERIMENTAL DATA
HAMSTERS
PH VALUE
SURVIVAL CURVES
TEMPERATURE EFFECTS
X RADIATION
ANIMAL CELLS
ANIMALS
BIOLOGICAL EFFECTS
BODY TEMPERATURE
CONNECTIVE TISSUE CELLS
DATA
ELECTROMAGNETIC RADIATION
INFORMATION
IONIZING RADIATIONS
MAMMALS
NUMERICAL DATA
RADIATION EFFECTS
RADIATIONS
RODENTS
SOMATIC CELLS
VERTEBRATES
560121* - Radiation Effects on Cells- External Source- (-1987)
560201 - Thermal Effects- Cells- (-1987)