Role of Food Consumption in the Mortality Response of Irradiated Rats Subjected to Prolonged Cold Exposure

¹ From the Division of Biological and Medical Sciences, U. S. Naval Radiological Defense Laboratory, San Francisco, California

Prolonged exposure to a low ambient temperature increases the 30-day mortality rate of irradiated rats. To determine if the increased mortality is due to a failure of the irradiated rat to adapt to the higher metabolic demands of a cold environment, the food consumption of irradiated (500r, 600r, 250 kv x-rays) animals was measured during 30 days of exposure at normal (23°C) or lowered (6°C) environmental temperature. The food consumption of irradiated animals was increased by exposure to cold; however, this increase was not sufficient to maintain body weight at a level comparable to nonirradiated animals. When the food consumption of nonirradiated animals was limited to that of irradiated animals during exposure to a 6°C environment, the mortality observed among nonirradiated animals was comparable to the increase in mortality induced by cold exposure of irradiated animals. These results suggest that the increased mortality rate of irradiated animals in a cold environment is related to an inadequate food intake.