THE EFFECT OF SERUM AMYLOID PROTEIN-A FRAGMENT-SAA(25-76) ON BLOOD-PLATELET AGGREGATION

The effect of the major acute phase protein serum amyloid A (SAA) on c ollagen induced platelet aggregation was investigated. A truncated ver sion of SAA, SAA(25-76) was tested for inhibitory capacity of collagen induced platelet aggregation in platelet-rich plasma (PRP) and whole blood (WB). The tetrapeptide RGDV, a known inhibitor of platelet aggre gation, was included as a reference compound. SAA(25-76) at a concentr ation of 390 mu g/ml inhibited platelet aggregation induced by 1 mu g/ ml of collagen in PRP. This corresponds to the plasma concentration of SAA during an acute phase response. However, the inhibitory effect of the SAA(25-76) fragment was lost at higher collagen concentrations (g reater than or equal to 2.0 mu g/ml). The SAA fragment at 390 mu g/ml had no significant effect on platelet aggregation in WB. In contrast, RGDV blocked collagen induced platelet aggregation in both PRP and WB.