Alpha granule explained

Alpha granule
Latin:	granulum alpha
Partof:	Platelets

Alpha granules, (α-granules) also known as platelet alpha-granules are a cellular component of platelets. Platelets contain different types of granules that perform different functions, and include alpha granules, dense granules, and lysosomes.^[1] Of these, alpha granules are the most common, making up 50% to 80% of the secretory granules.^[2] Alpha granules contain several growth factors.^[3]

Contents

Contents include insulin-like growth factor 1, platelet-derived growth factors, TGF beta, platelet factor 4 (which is a heparin-binding chemokine) and other clotting proteins (such as thrombospondin, fibronectin, factor V,^[4] and von Willebrand factor).^[5]

The alpha granules express the adhesion molecule P-selectin^[6] and CD63.^[7] These are transferred to the membrane after synthesis.

The other type of granules within platelets are called dense granules.

Clinical significance

A deficiency of alpha granules is known as gray platelet syndrome.

See also

• Platelet rich fibrin

Notes and References

1. Blair P, Flaumenhaft R . Platelet alpha-granules: basic biology and clinical correlates . Blood Reviews . 23 . 4 . 177–89 . July 2009 . 19450911 . 2720568 . 10.1016/j.blre.2009.04.001 .
2. Heijnen . H. . Sluijs . P. van der . Platelet secretory behaviour: as diverse as the granules … or not? . Journal of Thrombosis and Haemostasis . 3 April 2021 . 2141–2151 . en . 10.1111/jth.13147 . 2015. 13 . 12 . 26391322 . 206159932 .
3. Harrison P, Cramer EM . Platelet alpha-granules . Blood Reviews . 7 . 1 . 52–62 . March 1993 . 8467233 . 10.1016/0268-960X(93)90024-X .
4. Whiteheart SW . Platelet granules: surprise packages . Blood . August 2011 . 118 . 5 . 1190–1191 . 10.1182/blood-2011-06-359836. 21816838 . 8273132 . free .
5. Nurden AT . Platelets, inflammation and tissue regeneration . Thrombosis and Haemostasis . 105 . Suppl 1 . S13–33 . May 2011 . 21479340 . 10.1160/THS10-11-0720 . 36934086 .
6. Book: Stuart H. . Orkin . David G. . Nathan . David . Ginsburg . A. Thomas . Look . vanc . Nathan and Oski's hematology of infancy and childhood. 2 November 2010. 2009. Elsevier Health Sciences. 978-1-4160-3430-8. 1386–.
7. Book: William B. . Coleman . Gregory J. . Tsongalis . vanc . Molecular pathology: the molecular basis of human disease. 2 November 2010. 2009. Academic Press. 978-0-12-374419-7. 258–.