STUDIES ON THROMBOPOIESIS. III. THROMBOCYTOSIS-PROMOTING EFFECTS OF "THROMBOCYTHEMIC" AND "POLYCYTHEMIC" PLASMAS.

Abstract

Abstract Thrombocyte responses were determined in groups of normal rats given multiple daily doses by gastric tube of the thermostable fraction of plasmas from patients with primary thrombocythemia or polycythemia vera and from normal human subjects. Control animals received water by the same route. Increases of 60 to 70 per cent in the recipients' platelet counts appear to constitute maximum responses obtainable with this assay technique. Daily doses of the "thrombocythemic" and "polycythemic" plasma extracts equal to 2 ml. of the original plasma per 100 grams body weight evoked, respectively, 71 and 73 per cent increases in the rats' platelet counts. Comparable amounts of normal plasma induced a 36 per cent increase in the recipients' circulating platelets. When the daily dose was decreased to 1 per cent of the rats' weights, thrombocytosis-promoting activity was no longer detectable in normal plasma. Recipients of lesser quantities of the "thrombocythemic" plasma manifested thrombocytosis equivalent to that brought about by twice the dose. The route of administration, dose-response relationship, and restoration of normal counts after treatment was stopped attest to the specificity of the stimulus contained in these test materials. Plasmas from 19 additional patients with polycythemia vera have exerted similar thrombocytosis-promoting effects in normal rats. These data provide further support for the thesis that a humoral regulator (or regulators) exerts physiologic and pathophysiologic control over thrombopoiesis.