The effects of low dose (less than 1 rad) X-rays on the erythropoietic marrow.

Adult female Sprague-Dawley rats were exposed (200 kvp X-rays) to whole body doses of 22-1320 mrad and examined for changes in the level of red blood cell precursors (RBCp) in the marrow at 5-30 weeks post-irradiation, under nonbled and phlebotomy-induced anemic stress conditions. Increases in the RBCp %, RBCp/mg marrow, and RBCp/skeleton under nonbled conditions, and a suppressed erythroid response to an induced anemia, were found after acute doses in the range of at least 70 mrad. Dosages of 22 or 44 mrad that induced no measurable changes when applied only once were found to be effective when they were employed 4 or 2 times/week, respectively. The results suggested the presence of a linear-quadratic dose-response relationship in which the quadratic function exists between 88 and 981 mrad, and the linear dependency, below 88 mrad.