Organ Weight Analysis in Mice Given Fractionated X-Irradiation

Abstract

Although certain effects of single and repeated exposures to irradiation on organ weights of growing animals are known (1-4), these studies have been rather limited in scope, and no data could be found with irradiation intervals greater than 1 day. Body weight loss is known to be a manifestation of radiation injury, and, except for radiosensitive organs such as spleen and thymus, the amount of organ weight loss is a function of body weight loss. The purposes of these experiments were to determine mean values and their variances for a large number of body dimensions and organ weights of growing mice, X-irradiated at weekly intervals and at various dosage rates until maturity, and to relate the amount of weight change with these periodic exposures to radiation. The combined data are the results of three separate experiments (Table I). The original experiment included the individual body dimensions in addition to organ weights. Since the body and appendage measurements showed no significant deviation from the controls, these data are not included in this paper, although they have appeared in a previous report (5). It was noted in the first experiment that the spleen weight failed to show the constant decline with increasing dose characteristic of other radiosensitive organs. Because of increasing interest in the role of the spleen in radiation injury (6, 7), the second and third experiments were designed to gain more information about radiation effects on the spleen, by means of histological, hematological, and area-mapping methods. The organ weight changes are presented as changes that occur independently of changes in body weight. Proportionality of body and organ weight change is obtained by the use of the logarithms of the weights. The regressions of organ weights on dose with respect to the rotated or transformed axis are presented.