Effects of Protracted Irradiation in the Blood-forming Organs of the Rat. Part I: Continuous Exposure

Abstract
A study has been made of the changes in the blood and bone marrow of rats subjected to continuous irradiation from a 137Cs source at dose-rates from 16 rads/day to 415 rads/day. At dose-rates of 84 rads/day and below there is a recovery in platelets and white cells after an initial fall. This recovery commences at about 20 days after the start of irradiation and at 84 rads/day is only transient. At 50 rads/day and below, however, near normal levels of blood count are maintained for a long period of time. Splenectomy profoundly affects the pattern of change, particularly with respect to the platelet level and the level of mononuclear leukocytes. Possible mechanisms for the maintenance of a steady state under continuous irradiation are discussed in relation to similar findings in the response of the intestinal epithelium.