Absence of Effect of DDAVP Infusion on Platelet Glycoprotein Ib/IX and IIb/IIIa Complexes, and their Interaction with Newly Released von Willebrand Factor

Quality assessment of platelet concentrates supplemented with second-messenger effectors

BACKGROUND

While reducing the potential for bacterial contamination, the storage of platelet concentrates (PCs) at refrigerated temperatures is not routine, because of the induction of the so-called platelet storage lesion. As the modulation of second-messenger levels might help to overcome this drawback, a quality assessment of PCs treated with a mixture of second-messengers effectors known as ThromboSol was performed.

STUDY DESIGN AND METHODS

The PCs were supplemented with ThromboSol or phosphate-buffered saline, and stored in parallel at 22 degrees C with continuous agitation or at 4 degrees C. At 1, 5, and 9 days, an in vitro quality assessment of the PCs was performed, including measurement of cell number, metabolic and integrity markers, platelet surface expression of glycoproteins, platelet response to ristocetin and thrombin, and levels of cyclic adenosine 3', 5' monophosphate (cAMP) and thromboxane B2 (TxB2).

RESULTS

Control PCs stored at 4 degrees C underwent aggregation and displayed a significant decrease in the platelet number (40% on Day 5). By contrast, the ThromboSol-treated PCs maintained 80 percent of their initial platelet concentration after 9 days of storage at 4 degrees C. Compared to PCs stored at 22 degrees C, refrigerated PCs exhibited minor changes in metabolic values throughout storage, but the addition of ThromboSol induced a rise in metabolic rate during storage at 22 degrees C. Platelet responsiveness to both ristocetin and thrombin was maximally preserved in the ThromboSol-treated PCs stored at 4 degrees C. These units also maintained high levels of cAMP and low concentrations of TxB2 during storage.

CONCLUSION

The pharmacologic supplementation of PCs with ThromboSol significantly favors the maintenance of in vitro integrity and responsiveness of platelets during extended storage at refrigerated temperature. This protective effect seems to be a consequence of the ability of ThromboSol's components to sustain high levels of cAMP and to inhibit TxB2 production during the entire extended-storage period.

Stability of glycoproteins Ib/IX and IIb/IIIa during preparation and storage of platelet concentrates: detection by binding assays with epitope-defined monoclonal antibodies and physiological ligands

Preservation of the glycoprotein (GP) complexes Ib/IX and IIb/IIIa, because of their role as specific platelet receptors for adhesive proteins, is essential for the haemostatic efficacy of transfusions of platelet concentrates (PCs). We have combined binding assays with epitope-defined monoclonal antibodies, and with the physiological ligands von Willebrand factor and fibrinogen (Fo), to investigate the total expression and functional status of these receptors, in PCs stored for up to 9 days. Routine preparation and storage for up to 5 days have no apparent effect on the surface expression and the functional status of GPs Ib/IX and IIb/IIIa. However, after prolonged storage for up to 9 days we found a 50% decrease in the level of the total and functional GP Ib/IX content of platelets. This finding parallelled a significant rise in plasma glycocalicin, a proteolytic fragment of GP Ib. In addition, long-term storage promoted an impairment in the exposure of GP IIb/IIIa to Fo, and a 50% decrease in Fo binding capacity, without affecting the complex quantitatively. Finally, we also noticed a storage-induced increase in the platelet surface expression of GMP 140, and after 9 days of storage there was a rise in mean platelet volume, and a significant reduction in pH levels.