Dense granule Information & Dense granule Links at HealthHaven.com

Dense granules (also known as dense bodies or delta granules) are specialized secretory organelles. They contain adenine nucleotides (ADP and ATP), ionized calcium, histamine, serotonin, and epinephrine.

It accomplishes this by inducing the conformational change of platelets' GpIIb-IIIa receptor so that they can bind fibrinogen. Fibrinogen acts as a crosslink between the platelets allowing aggregation. ADP also induces other platelets to degranulate potentiating coagulation. In other words, ADP stimulation, in conjunction with thromboxane A₂ and thrombin, causes platelet aggregation and the formation of a secondary hemostatic plug (the "second wave"). Endothelial cells express adenosine dephosphatase which acts as an anti-coagulant by breaking down ADP and preventing the actions discussed above.

The drug clopidogrel (Plavix) antagonizes the platelet ADP receptor and inhibits the "second wave" effect of aggregation.

Other molecules within platelet dense granules include adenosine triphosphate (ATP), ionized calcium which is necessary for several steps of the coagulation cascade, histamine which acts as a vasodilator, serotonin, and epinephrine.

Apicomplexa protozoans have dense granules.

Summary -- dense granules contain: ADP/ATP, calcium, serotonin.

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[edit] External links

dense+bodies at eMedicine Dictionary
Nishibori M, Cham B, McNicol A, Shalev A, Jain N, Gerrard J (1993). "The protein CD63 is in platelet dense granules, is deficient in a patient with Hermansky-Pudlak syndrome, and appears identical to granulophysin.". J Clin Invest 91 (4): 1775–82. doi:10.1172/JCI116388. PMID 7682577.

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