THE EFFECT OF HEMATOPOIETIC GROWTH-FACTORS ON PLATELET AGGREGABILITY

We compared the in vitro effect of thrombopoietin (TPO) on platelet ag gregation to other hematopoietic growth factors (HGFs): granulocyte co lony stimulating factor (G-CSF), granulocyte macrophage colony stimula ting factor (GMCSF), interleukin-3 (IL-3), interleukin-6 (IL-6), and e rythropoietin (EPO). The platelet aggregation response of the venous b lood of eight volunteers with differing aggregation patterns was chara cterized by a platelet aggregation (PA) score that provided numerical assessment of an individual's platelet aggregation tendency to adenosi ne diphosphate (ADP). The method for analysis of the data included con structing regression lines for each participant's PA score versus the HGF concentration (range of 0.5 nG/mL to 100 nG/mL) and calculating th e regression coefficients for the slope and the Y axis intercept. We d emonstrated that the proposed method resulted in accurate assessment o f the HGF effect or lack of it on the platelet aggregation response. W ithin the concentration range evaluated, the influence of IL-6 and G-C SF on platelet aggregability was insignificant and the effects of GM-C SF and IL-3 were almost undetectable. In contrast, the potentiating ef fect of TPO on platelet activation was dose dependent with significant enhancement for all responder types. The concentrations of TPO utiliz ed in our in vitro experiments were in pathophysiological range, indic ating that its impact on platelet aggregation may have clinical releva nce, and that monitoring platelet function in conjunction with TPO tre atment might be advisable. Investigation of the possible synergistic e ffect of HGF combinations is warranted.