[Data on humoral regulation of thrombocytopoiesis]

Biological testing on intact and splenectomized dogs were made to study thrombopoietic activity of the blood in the course of developing drug thrombocytopenia. It is shown that intact dogs' blood contains a thrombopoietin inhibitor inducing the reduction in the mouse platelet count 48 hours after the dog serum injection. In rubomycin model of drug thrombocytopenia, thrombopoietic blood activity increased only after the fall of platelet count by 30% or still more compared to the baseline level. In splenectomized dogs the thrombopoietin inhibitor was not detected, a moderate rise in thrombopoietic activity occurred within 7 weeks. Thrombocytopenia modelling in these conditions requires double cytostatic dose and longer time in spite of less pronounced thrombocytopenia, thrombopoietic activity enhancing to the same degree as without the cytostatic. It is suggested that the spleen produces thrombopoietin inhibitor which links thrombopoietin with megakaryocyte potentiator.