Glycoprotein HB - IHA and RGD ( S ) Are Not Important for Fibronectin - Dependent Platelet Adhesion Under Flow Conditions

Previous studies have indicated that activated blood platelets interact with fibronectin through binding of fibronectin to the glycoprotein llb-Illa complex (GPIIb-llla). The cell attachment site of fibronectin with its crucial arg-glyasp(-ser) [RGD(S)]sequence is involved in these bindings. We studied the importance of these interactions for the fibronectin dependence of platelet adhesion under flow conditions. An RGDS-containing hexapeptide (GRGDSP) was compared with a nonreactive control peptide (GRGESP). The GRGDSP-peptide inhibited thrombininduced aggregation and adhesion under static conditions at 0.1 mmol/L. This concentration had no effect on platelet adhesion to nonfibrillar collagen type I in flow. GRGDSP at 1 mmol/L had a significant inhibitory effect at 1.500 s . but not at the lower shear rates of 800 and 300 s’ where platelet adhesion is also fibronectin dependent. On the matrix of cultured human umbilical vein endothelial cells. 1 mmol/L GRGDSP had no effect on platelet adhesion. The