Effects of Internal Irradiation of Mice with P32

Publisher Website
Google Scholar
Abstract
The accumulation of accurate data on radiation injury resulting from internal radioactive materials is of utmost importance. Such information will aid in outlining radioactive isotope therapy for cancer and other conditions and in formulating a therapeutic program in the event of human injury from internal radiation. It is the purpose of this study to determine the radiation effects in mice injected with P32. The mouse was selected as a subject because of its extreme radiosensitivity, which is somewhat comparable to the degree of radiosensitivity in man. In studying the effects of continuous radiation from a substance spread throughout the body tissues, it is necessary for evaluation of the changes produced in them, and determination of their radiosensitivity, not only to describe morphologic changes ascribed to radiation effect but also to know the general pattern of radiation intensity. The pattern of radiation intensity in the tissues depends upon two factors: first, the physical characteristics of the radiation; second, the chemical properties of the radioactive material. The degree of retention and the rate of excretion, as well as the localization and concentration of the radioactive material within special tissues, depend on its chemical properties. The radiations from P32 are moderately soft beta rays with an average mev of 0.7; they are completely absorbed by 8 mm. of tissue, and 50 per cent absorbed by 3 mm. of tissue. Determinations of diffusion, partitioning, and excretion of P32 have been made on rats, rabbits, and mice (5). The distribution in the tissues of normal and leukemic patients has also been determined (3, 4). These studies indicate that for several days after injection the visceral organs, especially the liver and spleen, have the greatest concentration of the isotope. After the first few days, however, the P32 content of these organs decreases and the greatest concentration is in the bone. About two weeks after injection, little or none is to be found in the visceral organs, but the bones retain significant amounts for more than five weeks. The P32 is laid down most rapidly in growing bone. Since the mice used in our work were adult, there would be little bone growth, and this would result in an almost equal distribution of P32 throughout the skeleton. Bone and bone marrow would receive the greatest amount of radiation, with moderate amounts reaching tissues adjacent to and within 2 to 4 mm. of sizeable bones, and the smallest amounts reaching tissues well removed from the bones. The first part of this study is concerned with the spleen, lymph nodes, thymus, bone, and bone marrow. Materials and Methods Eighty-two adult Swiss strain mice averaging 31 gm. were divided into four groups.