REGULATION OF MEGAKARYOCYTE PLOIDY INVIVO IN THE RAT

  • 1 January 1990
    • journal article
    • research article
    • Vol. 75  (1) , 74-81
Abstract
The relationship between the bone marrow (BM) megkaryocyte and the circulating platelet was explored. Incremental changes in platelet count were made in rats by infusion of antiplatelet antibody or by platelet transfusion, and the response of megakaryocytes was measured by flow cytometry. Proportional changes in megakaryocyte ploidy were demonstrated: As the platelet count declined, ploidy increased; as the platelet count increased, ploidy decreased. Even moderate degrees of thrombocytopenia and thrombocytosis (48% and 177% of the normal platelet count) were associated with changes in ploidy. These changes were not the results of the technique used to alter the platelet count because reinfusion of platelets after 3 hours of thrombocytopenia prevented any ploidy change. These studies proved that the circulating platelet and the megakarycyte constitute a classic feedback loop whose activity can be measured by the degree of ploidization of the megakaryocyte. The minimal duration of thrombocytopenia necessary to promote megakaryocyte ploidy changes was approximately 10 hours. Using a BM culture assay, we identified a plasma factor which induces alterations in megakaryocyte ploidy and whose level in inversely proportional to the platelet count.