Morphologic Platelet Changes in Vitro and During Thrombus Formation in the Rat

Abstract

Using high power Nomarski optics the shape change of thrombocytes can be shown. Platelets appear in their native shape as flat discs, less than 25% show pseudopodes. Depending on the time after blood sampling and on incubation temperature platelets in PRP or citrated blood swell and form tentacles. The addition of ADP to PRP induces the formation of aggregates. Single platelets form large vesicles rupturing and releasing granulated material. The remaining platelet material fuses. Bencyclan affects platelet morphology by inducing a spherical transformation, which is paralleled by the inhibition of platelet adhesiveness, spreading and aggregation. Observations in small mesenteric vessels of the rat show platelets in their native shape under stasis conditions. Vascular lesions are produced with a focused laserbeam (Hadron 513 biolaser). Immediately after the lesion platelets stick to the site of the microburn. Within seconds these platelets swell and form protrusions. After 3 - 10 min the vessel is occluded by a thrombus, of platelets, which undergo further swelling. Later the thrombus is partially or completely swept away and the vessel is recanalized. Irreversible fusion of platelets is rarely observed. These morphologic platelet changes differ markedly from those observed during in vitro aggregation. Injection of a new antithrombotic substance (Bay G 6575) diminishes the adhesion of platelets on the vessel lesion. The morphologic changes of single platelets (primary shape change) probably represent basic processes in hemostasis and thrombus formation.