Morphological Analysis of Adherent Platelets: Influence of Platelet Inhibitors or Antineoplastic Agents on Platelet Adhesion

Platelets adhere to many, but not all, non-platelet surfaces including artificial surfaces, collagen, and subendothelium. Many different methods have been used to study platelet adhesion. But, many questions concerning mechanisms of platelet adhesion remain unanswered.In this study, the glass bead column method, the method of collagen-sepharose assessment of platelet adhesiveness to collagen fibers, and the method for the measurement of platelet adhesiveness to the subendothelium using the flow chamber system according to Baumgartner were used. Morphology of adherent platelets and their adhesiveness were investigated and compared with normal controls and blood treated with platelet inhibitors or antineoplastic agents by these various methods. Acetylsalicylic acid (ASA), Dilazep. (DZP), or the combination of ASA and DZP, as platelet inhibitors and Daunorubicin (DNR) or Doxorubicin (DXR)as antineoplastic agents were used.By the glass bead column method, platelet retention rate was reduced in these treated bloods at high concentrations. Scanning electron microscopy (SEM) revealed that adherent platelets of these treated bloods on the glass surfaces had no remarkable changes as compared with controls; however, the number of aggregates was reduced.By the method of adhesiveness to collagen-sepharose, the effect of these platelet inhibitors or antineoplastic agents was not significiant. No change in morphology of adherent platelets of these bloods treated with collagen fibers was seen as compared with controls.By Baumgartner's method, by SEM, adherent platelets of the bloods treated with platelet inhibitors at the subendothelium had extended pseudpods and were spread out as much as normal controls. But, platelet thrombus formations were significantly reduced. Antineoplastic agents inhibited spreading out of adherent platelets at the subendothelial surface, and DNR S-2also inhibited the extending pseudopods.By transmission electron microscopy (TEM), platelets associated with the subendothelial surface had lost most of their granules; those from normal controls were more affected than treated blood. With antineoplastic agents, adherent platelets at the subendothelial surface were observed to retain the *g r anules and the ring of microtubules in the marginal zone, and then to have a swollen aspect. Platelet adhesion to the subendothelium and thrombi were confirmed and quantitated by light microscopical morphometric technique.