Abstract
Morphological aspects of the platelet release reaction induced by ADP and/or Teleocidin (tumor promoter) in the presence or absence of aspirin were studied by transmission electron microscopy. Human platelet-rich plasma (PRP) treated with reagents at 37°C for 1-5min was fixed with aldehyde and embedded in Epon or Lowicryl K 4 M. Addition of ADP (10μM) resulted in the centralization of granules without granule release, while Teleocidin (100ng/ml) induced the swelling of the open-canalicular system and the release of α-granules without centralization of these granules. When both ADP and Teleocidin were added, the synergetic effect was predominant and all of the granules were discharged from the cytoplasm. The results were essentially the same both in the presence and absence of aspirin. Post-embedding immunocytochemical studies employing protein A-gold as a label revealed that several components of α-granules, e. g., β-thromboglobulin, platelet factor 4, but not the dense-granule component, serotonin, moved into the swollen open-canalicular system following the administration of Teleocidin. In the case of the administration of both Teleocidin and ADP, both α-granular and dense-granular components moved into the swollen open-canalicular system.
