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Dense Bodies
From Wikipedia, the free encyclopedia
Dense bodies, also called delta granules, along with alpha granules are found within blood platelets. They contain adenine nucleotides ADP which are important for the aggregation of platelets in the formation of a hemostatic plug. 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. Furthermore, ADP in conjunction with thromboxane A2 and thrombin cause platelet contraction and the formation of a secondary hemostatic plug. Endothelial cells express adenosine dephosphatase which acts as an anti-coagulant by breaking down ADP and preventing the actions discussed above.
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, seratonin, and epinephrine.