STIMULATION OF MEGAKARYOCYTOPOIESIS BY ACUTE THROMBOCYTOPENIA IN RATS

  • 1 January 1976
    • journal article
    • research article
    • Vol. 48  (5) , 765-775
Abstract
Rats were made acutely thrombocytopenic by injection of antiplatelet serum. Marrow sections and squash preparations were made at intervals during 120 h. Determinations were made of mitotic index, stage of maturation, ploidy level and cell size of megakaryocytes; number and size of platelets were measured. Increased endomitosis among megakaryocytes was followed by an increase in the proportion of immature megakaryocytes, a greater average ploidy level of recognized megakaryocytes and larger megakaryocytes. Maximum changes in these several parameters occurred between 32 and 72 h after induction of thrombocytopenia. By 120 h all megakarocyte parameters were near normal. For about 3 days, beginning at about 36 h, platelet numbers increased rapidly. Average platelet size rose and returned to normal within about 60 h. Changes in ploidy and size of megakaryocytes were measured in the immature and mature maturation stages. The initial stimulus in response to acute thrombocytopenia apparently acted primarily on diploid precursors, programming them to mature into a population of megakarycytes with an average ploidy approximately 1 level greater than in normal rats and a proportionate increase in cell size. The larger megakaryocytes presumably produce more platelets, accounting for a major part of the increased rate of platelet production. Since the changes in meg akaryocytes began to reverse before circulating platelet numbers reached the normal level, reversal of the stimulus appeared to be initiated by some change other than platelet mass.

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