Stimulation of thrombocytopoiesis in irradiated mice.

A NUMBER OF OBSERVATIONS have suggested that megakaryocytopoiesis is subject to homeostatic control. The mechanism by which feedback regulation of platelet production may be mediated, however, has not been defined. One reason for this is that a reproducible, sensitive, and specific system by which humoral thrombopoietic substances could be assayed has not been described. In the past, a comparable problem confronted investigators studying the control of erythropoiesis. A significant advance was the demonstration that erythropoiesis was stimulated in sublethally irradiated animals which were acutely anemic or hypoxic during the immediate preor post-irradiation period.1 This modification of the radiation-induced erythroid suppression was shown to be due to the humoral factor, erythropoietin,2 and the animal in which erythropoiesis was suppressed by sublethal radiation proved to be a more sensitive assay system for erythropoietin than the intact animal.3 The experiments reported here were undertaken to determine if the thrombocytopoietic response to sublethal radiation would be affected by the presence of thrombocytopenia at the time of irradiation. A recent report indicates that the mortality from lethal irradiation and the thrombocytopenia from sublethal irradiation iiia ’ be modified by acute thrombocytopenia at the proper time prior to exposure to radiation.4