Exposure to heavy charged particles affects thermoregulation in rats

Rats exposed to 0.1-5 Gy of heavy particles (56Fe, 40Ar, 20Ne or 4He) showed dose-dependent changes in body temperature. Lower doses of all particles produced hyperthermia, and higher doses of 20Ne and 56Fe produced hypothermia. Of the four HZE particles, 56Fe particles were the most potent and 4He particles were the least potent in producing changes in thermoregulation. The 20Ne and 40Ar particles produced an intermediate level of change in body temperature. Significantly greater hyperthermia was produced by exposure to 1 Gy of 20Ne, 40Ar and 56Fe particles than by exposure to 1 Gy of 60Co gamma rays. Pretreating rats with the cyclo-oxygenase inhibitor indomethacin attenuated the hyperthermia produced by exposure to 1 Gy of 56Fe particles, indicating that prostaglandins mediate 56Fe-particle-induced hyperthermia. The hypothermia produced by exposure to 5 Gy of 56Fe particles is mediated by histamine and can be attenuated by treatment with the antihistamines mepyramine and cimetidine.