Effects of acetylsalicylic acid, sulfinpyrazone and dipyridamole on platelet adhesion and aggregation in flowing native and anticoagulated blood.

The interaction of rabbit platelets with subendothelium of rabbit aorta was investigated under controlled blood flow conditions. Platelet adhesion and thrombus formation were compared after perfusion of native blood and of blood anticoagulated with citrate, heparin or heparin plus citrate. 15 mM citrate in plasma caused significant reduction of aggregation, thrombus volume and thrombus height; adhesion was concomitantly increased. Heparin (500 U/kg) had no significant effect on adhesion and thrombus dimensions. Treatment of rabbits with acetylsalicylic acid or sulfinpyrazone caused a significant reduction of thrombus volume and thrombus height in the presence of citrate. However, no significant effects were observed in native or heparinized blood. It is concluded that low citrate concentrations: (1) inhibit thrombus growth; (2) enhance thrombus breakdown; (3) therefore increase adhesion, and (4) strongly enhance a possible inhibitory effect of acetylsalicylic acid and sulfinpyrazone on thrombus growth.