Plasma thrombospondin in patients with chronic renal failure, liver disease and splenectomy

Abstract

Thrombospondin (TSP), is a major constituent of human blood platelet alpha-granules. Stimulation of platelets causes the release of TSP in parallel with other alpha-granule constituents such as β-thromboglobulin (β-TG) and platelet factor 4 (PF4) but the thrombospondin plasma in vivo half life is significantly greater than β-TG and PF4. The aim of this study was to assay TSP levels in plasma of patients with chronic renal failure (CRF), liver disease (LD) and following splenectomy. The TSP values were then compared to the patients plasma levels of two traditional markers of platelet activation, β-TG and PF4, and to fibronectin (FN) and von Willebrand factor (VIII:vWF). Plasma TSP levels (67.6 ± 16.9 ng/ml) assayed in 14 CRF patients were significantly higher (p<0.05) than those measured in 28 donors (55.5 ± 11.7 ng/ml). No correlation was observed, in CRF patients, between the TSP level and PF4 (2.5 ± 1.5 ng/ml), β-TG (131.1 ± 21 ng/ml), FVIII:vWF (252 ± 85%), or FN (102 ± 33%) plasma levels. The TSP plasma level in CRF patients was significantly correlated (p<0.02) with that of fibrinopeptide A (4.1 ± 1.9 ng/ml). Although the β-TG (23.5 ± 6.9 ng/ml) and PF4 (2.9 ± 2ng/ml) plasma levels in six LD patients were normal, the TSP levels (82.5 ± 39.1 ng/ml) were significantly increased (p<0.01). Thrombospondin plasma levels (77.1 ± 20.1 ng/ml) in 14 patients having undergone splenectomy were significantly increased (p<0.001). In addition PF4 (4.6 ± 2.1 ng/ml) and FN (116 ± 51%) plasma levels, but not β-TG (22.7 ± 7.9 ng/ml) were increased. It is concluded that, great care has to be taken in interpreting the TSP plasma levels, since increase in pathological situations may not be related to platelet release.