Kinetics of Colchicine-Induced Hemopoietic Recovery in Irradiated Mice

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Abstract
The recovery of bone marrow and splenic hemopoiesis was studied in irradiated mice given colchicine either 2 days before or shortly after whole-body irradiation. The preirra-diation treatment accelerates both marrow and splenic regeneration, with resulting increased survival due to early recovery of normal granulocyte levels. Postirradiation treatment accelerates splenic erythropoietic regeneration, but fails to improve marrow regeneration, resulting in persistent granulocytopenia and in death rates similar to that found in the controls. Colony-forming units [CFU], as assayed by Till and McCulloch''s method, responded similarly. They recovered earlier in the marrow of the pretreated animals, but failed to do so in the marrow of mice that received colchicine after irradiation. In contrast, the time of recovery of splenic CFU was advanced with postirradiation treatment as well as with treatment given 2 days before irradiation. The observations presented add to the mounting evidence that either committed and noncommitted stem cells exist, or a single stem cell can undergo physiologic changes that alter its potentials for transplantability and differentiation. To decide between these alternatives will require extensive further exploration.