The effect of serum amyloid protein A fragment-SAA25-76 on blood platelet aggregation

The effect of the major acute phase protein serum amyloid A (SAA) on collagen induced platelet aggregation was investigated. A truncated version of SAA, SAA25-76 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 aggregation, was included as a reference compound. SAA25-76 at a concentration of 390 micrograms/ml inhibited platelet aggregation induced by 1 microgram/ml of collagen in PRP. This corresponds to the plasma concentration of SAA during an acute phase response. However, the inhibitory effect of the SAA25-76 fragment was lost at higher collagen concentrations (> or = 2.0 micrograms/ml). The SAA fragment at 390 micrograms/ml had no significant effect on platelet aggregation in WB. In contrast, RGDV blocked collagen induced platelet aggregation in both PRP and WB.