Adenosine 5’-diphosphate (ADP) is the most important signaling molecule and it plays a key role in hemostasis and the development and extension of arterial thrombosis. ADP was the first low molecular weight agent recognized to cause platelet aggregation.
NTPDases and adenylate kinase (AK) are the main enzymes involved in metabolism of extracellular adenine nucleotides. The majority of studies was concentrated on the role of apyrase in the inhibition of platelets activation. Up to now, there are no experiments on the role of adenylate kinase in this process.
We studied the influence of aggregation agents: ADP (20 μM) and collagen (7,5 μg/ml) on platelet aggregation from pig blood. Both compounds activate aggregation of platelets in the citrated platelet-rich plasma (PRP). 1U of apyrase and AK activity added to PRP before ADP or collagen, inhibits the platelet aggregation. One minute after adding of ADP or collagen as much as 5U of apyrase and adenylate kinase is necessary for stopping of the platelet aggregation.
The infuence of apyrase and adenylate kinase on metabolism ADP was analysed by high-performace liquid chromatography (HPLC) metod. Products of degradation of purines by apyrase and AK are different. In the presence of apyrase activity ADP was converted to AMP but we also observed increased level of adenosine compared to control (PRP + 20 μM ADP). This may be due the fact that apyrase from Sigma Corporation has got a lot of 5’-nucleotidase activity. In the presence of adenylate kinase activity, products of the reaction were AMP, ATP and IMP.
These data suggest that investigated enzymes play an important role in the pathogenesis of cardiovascular system. Anticoagulation role of apyrase and adenylate kinase indicate the possibility to using these enzymes as antithrombotic drugs in the treatment of arteriosclerosis and heart diseases.

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