Platelet–foreign surface interactions: Release of granule constituents from adherent platelets

The interaction of suspensions of washed pig platelets with nine artificial surfaces (glass, polystyrene, three segmented polyurethanes, and surfaces formed by coating glass with albumin, fibrinogen, gamma-globulin, and collagen) is reported. Platelet adhesion and release from adherent platelets were measured via labeling with 51Cr and 14C-serotonin. The apparatus was a couette flow device allowing observation of surface-platelet effects uncomplicated by transport or flow effects. Using a two-level factorial design the effects of albumin, fibrinogen, red cells, and platelet count on adhesion and release were estimated for each surface. Comparison of the various surfaces showed that collagen and gamma-globulin are the most reactive (mean adhesion, 34 platelets/100 micrometer2, mean release 50% of granule contents). The other surfaces showed lower levels of release (approximately 25%), indistinguishable one from another. The adhesion levels of two hydrophilic polyurethanes and albumin were low, while those of the remaining surfaces were moderate. The effect of albumin was to reduce adhesion for the "moderate" group of surfaces. Fibrinogen increased adhesion to nonprotein surfaces and decreased release for collagen and gamma-globulin surfaces. High platelet count increased adhesion to fibrinogen, gamma-globulin, and collagen surfaces. Red cells increased adhesion to all surfaces and increased release for collagen and gamma-globulin.