notes on platelet alpha granules exocytosis

arrested exocytosis of a disintegrating, vesiculating alpha granule in an activated platelet.

more on platelet exocytosis here;

• Polasek J. The appearance of multivesicular structures during platelet activation as observed by scanning electron microscopy. Thromb Res 1982; 28: 433-437. and 30: 183-184. 
• Polasek J. Release of multivesicular bodies from platelets as observed in SEM. Haematologia 1984; 17: 267-279. 
• Polasek J, Richardson M, Moore MA, Blajchman MJ. Evidence for an alternate mechanism of platelet secretion involving peripheralization of secretory granules and formation of membrane- associated multivesicular structures. Thromb Res 1987; 45: 771-782. 
• Polasek J. Lysosomal concept of platelet secretion - revisited. Eur J Haematol 1989. Suppl 50; Vol 43.
• Polasek J. Acetylsalicylic acid and vitamin E in prevention of arterial thrombosis. Can J Cardiol 1997;13:533-535.
• Polasek J. Procoagulant potential of platelet alpha granules. Platelets 2004;15(7):403-407.
• Polasek J. Platelet secretory granules or secretory lysosomes? Platelets 2005;16(8):500.Letter to the editor.
• Polasek J. Three modes of platelet degranulation? Pathophysiol Haemos Thromb 2006;35:408-409. Letter to the editor.
• Polasek J. Platelet lysosomal acid phosphatase enzyme activity as a marker of  platelet procoagulant activity. Blood Transfus 2009;7:155-156. Letter to the editor.
  

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has unique properties: it is firmly bound to its phospholipoprotein carrier, from which it cannot be solubilized even with Triton X-100. This phospholipoprotein labeled by acid phosphatase appears to have procoagulant properties, so called PF3.

• Polasek J. Particulate nature of acid phosphatase released from platelets. Thromb Diath Haemorrh 1968; 19: 466-473. 
• Polasek J, Kubisz P. Acid phosphatases and platelet factor 3. Scand J Haematol 1968; 5: 390-400. 

Acid phosphatase  and PF3 activities show direct correlation and the same individual variations in response to activation  as demonstrated in this graph.  For PF3 Russell's viper venom method was used.

On the other hand total amount of detectable platelet lysosomal activity in the presence of Triton X-100 appears fairly constant between individuals as demonstrated in this graph.