Reduction of rat thymocyte interphase death by hyperthermia

The effects of hyperthermia on rat thymocytes subjected to 1 kR irradiation were examined. Radiation-induced interphase death (judged by dye staining and ATP decline) observed after 4 hr of incubation of 370C following irradiation was reduced by exposing the cells for 30 min to 1 hr to 430C immediately before or after irradiation. Hyperthermia treatment at a lower temperature (such as 410C) was also effective in inducing cell recovery from radiation damage, although a longer treatment was needed. Hyperthermia administered 2 h after irradiation was ineffective and even enhanced cell death. To elucidate the mechanism underlying the effect, [14C]adenine and [32P]orthophosphate were used to estimate changes in ATP metabolism after heat exposure. Heat alone stimulated both ATP synthesis and degradation regardless of irradiation. Radiation-induced ATP degradation was markedly depressed by heat treatment