Residual radiation injury: impaired regrowth of realimented hypocalorically reared rats

¹ U. S. Naval Radiological Defense Laboratory, San Francisco, California

Hypocalorically reared rats were subjected to single exposures of X ray ranging from 400–700 rad or to repetitive exposures of 200 rad in four doses spaced 1 week apart (total 800 rad). They were allowed to recover for a minimum of 7 weeks and a maximum of 6 months after the last exposure and then returned to an adequate caloric intake. Realimentation of the irradiated populations resulted in reduced regrowth when compared to nonirradiated realimented rats of the same age. The reduction in regrowth persisted regardless of radiation exposure patterns, realimentation patterns, or the recovery periods here employed. Paired feeding demonstrated that the regrowth reduction is primarily one of reduced nutrient utilization. Gastrointestinal tract shielding showed that injury to the intestinal region with impaired absorption is probably not the cause. It is concluded that the reduced regrowth of the irradiated realimented rats is a generalized deficiency of nutrient utilization by the organs and tissues, perhaps mediated through the endocrines.