Diurnal Rhythmicity in the Sensitivity of Haemopoietic Cells to Whole-body Irradiation of Mice

Abstract

SummaryWhen mice are maintained on a light-dark cycle in which the light begins at 06.00 and ends at 18.00 hours, endogenous spleen colony-forming cells are most radiosensitive at 02.00 and most radioresistant at 22.00 hours. There are three cycles of radiosensitivity with a cycle time of 8 hours. The results are discussed on the basis of the cellular kinetics of the haemopoietic cell system.