In Vivo Platelet Release in Myeloproliferative Disorders

Abstract

SummaryThe in vivo platelet release reaction in 22 patients with myeloproliferative disorders has been studied by measuring plasma concentrations of the platelet release product β-throm-boglobulin (βTG). Mean βTG and mean βTG:whole blood platelet count ratio were significantly raised in the patient group taken as a whole compared to an age matched control group. No significant increases were observed in the plasma concentrations of thrombin and plasmin sensitive fibrinogen fragments fibrinopeptide A (FpA) and Bβ1-42. The patients were divided into those who had normal, increased or decreased responses to in vitro ADP-induced platelet aggregation. Mean βTG and the mean βTG:whole blood platelet count ratio were higher in the increased and decreased responders to ADP than in the normal aggregation group, but the differences in means were not statistically significant. Aspirin given to six patients at a dose sufficient to eliminate the secondary phase of ADP-induced platelet aggregation reduced mean βTG and the mean βTG : whole blood platelet count ratio but did not alter mean FpA and Bβ1-42. It is concluded that the enhanced platelet release reaction seen in myeloproliferative disorders is independent of plasma protease activity that arises when coagulation and fibrinolytic systems are activated.

Bleeding and Thrombosis in Chronic Myeloproliferative Disorders: Relation of Platelet Disorders to Clinical Aspects of the Disease

“…The facts that increased plasma levels of a-granule proteins were found in all patients and that PF4 plasma levels were correlated with the platelet count suggest that increased levels of a-granule proteins in MPD patients do not necessarily indicate platelet activation in the circula tion, but rather, the inability of MPD plate lets to store these proteins properly. The lack of significantly elevated FPA levels is in agreement with this hypothesis and corrobo rates results obtained by Ireland et al [ 1982] who found normal or slightly increased lev els of the fibrinogen fragments FPA and B(i 1-42 despite increased a-granule release. However, platelet function disorders in MPD patients may be related to abnormali ties of platelet morphology as there was con siderable variation of platelet volume heter ogeneity between patient subgroups.…”

Relationships between thrombohemorrhagic complications and platelet function in patients with essential thrombocythaemia

“…These observations are compatible with those of Ireland [16] who has shown an increase of ␤TG and PF4 in the overall group of ET patients. Thus, these disturbances cannot be linked with the variability of clinical complications among ET patients.…”

Clinical Significance of Beta-Thromboglobulin in Patients with High Platelet Count

“…The amount of serotonin stored in platelet-dense bodies is, in fact, statistically reduced in patients with MPD [5,9], whereas normal content of alpha granules has been reported [15]. Other studies demonstrate, in patients with MPD, high amounts of circulating ¡kg [7,13,16] and low content in alpha granules [4] as a consequence of the platelet activa tion in vivo. Our findings confirm the re duced content of serotonin in patients with MPD, but the results of the measure ment of (kg require further explanations.…”