Acute mild hypothermia caused by a low dose of X-irradiation induces a protective effect against mid-lethal doses of X-rays, and a low level concentration of ozone may act as a radiomimetic.
Acute changes in core body temperature following exposure to a low dose of X-rays were assessed in unanaesthetized and unrestrained mice. Radiotelemetry techniques were used to monitor core body temperature continuously. Following exposure to a 20 cGy dose of X-rays, the mice displayed a rapid and significant reduction in core body temperature relative to the sham-treated (non-irradiated) control animals. The present studies, and those by others, showed that pre-exposure to X-rays at doses as low as 20 cGy may result in a reduced mortality rate following subsequent exposure to X-rays at mid-lethal dose levels. This indicates an increased tolerance to radiation. An additional experiment was conducted to examine whether the reduction in the mortality rate following exposure to mid-lethal doses of radiation could be found when mice were subjected to a stressor, ozone inhalation, which induced a suppression in body temperature. The results showed that following inhalation of ozone at a concentration of 0.5 ppm, 93% of the treated animals survived a mid-lethal dose of radiation, whereas 50% of the sham-control animals died within 30 days. These results suggest that low-dose-induced tolerance to radiation may be dependent on a brief exposure to ozone, and a reduction in core temperature may be necessary to obtain tolerance effects in response to a mid-lethal dose of radiation.
Miyachi
Y
Y
Department of Physiology, Toho University School of Medicine, Tokyo, Japan.
D000208:Acute Disease; D000818:Animals; D001831:Body Temperature / Q000528:radiation effects*; D007036:Hypothermia, Induced / Q000379:methods*; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D010126:Ozone / Q000627:therapeutic use; D011836:Radiation Tolerance; D011837:Radiation-Protective Agents / Q000627:therapeutic use
D011837:Radiation-Protective Agents; D010126:Ozone