Size Dependent Platelet Subpopulations: Relationship of Platelet Volume to Ultrastructure Enzymatic Activity, and Function

摘要

A method for the separation of platelets on the basis of their size has been developed using counterflow centrifugation. Platelets were separated, free of plasma proteins and other cells, into 7 subpopulations. The smallest-sized platelets, designated as Fraction 1, had a mean platelet volume (MPV) of 3.94 + or - .60 cu microns (SD). Platelet function was measured by ADP-induced aggregation, serotonin uptake, and thrombin-induced release. Progressively more rapid and more complete aggregation was observed as the platelet size increased over the 7 fractions. Serotonin uptake was 4.2 times greater in the Fraction 7 platelets than in the Fraction 1 platelets. Quantitative release of serotonin following thrombin stimulation was significantly greater in the larger-sized platelets than in the smaller-sizer platelets. The observed differences in platelet aggregation, dense body content, LDH activity, and serotonin uptake and release suggest that large platelets may be functionally more important than smaller platelets.