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Differential cytotoxic effects of hyperthermia below and above 43/sup 0/C alone or combined with x irradiation

Journal Article · · Radiat. Res.; (United States)
DOI:https://doi.org/10.2307/3575638· OSTI ID:5678036
The effect of hyperthermia alone or combined with X irradiation on the proliferative capacity of CHO cells was studied for temperatures between 41 and 46/sup 0/C. For heat treatments in the range 41-43/sup 0/C or 43-46/sup 0/C, the Arrhenius plot yielded an inactivation energy of 417 +/- 28 and 167 +/- 16 kcal/mole, respectively. Hyperthermia at 42 and 45/sup 0/C, which by itself killed 10% of the cells, was combined with single X-ray doses ranging up to 7 Gy or with fractionated irradiation with two doses of 3 Gy. A mathematical description was developed to determine the effect of hyperthermia on repair of sublethal damage. At 37/sup 0/C sublethal damage was repaired with a half-time of 43.3 min. At 42/sup 0/C, hyperthermia accelerated the fixation of damage and enhanced repair of remaining sublethal damage, reducing the half-time to 19.3 min. In contrast, hyperthermia at 45/sup 0/C did not affect fixation of damage but depressed the rate of repair of sublethal damage, thus increasing the half-time to 83 min.
Research Organization:
Univ. of Hamburg, Federal Republic of Germany
OSTI ID:
5678036
Journal Information:
Radiat. Res.; (United States), Journal Name: Radiat. Res.; (United States) Vol. 88:3; ISSN RAREA
Country of Publication:
United States
Language:
English