Mast cells are mostly known for their important role in the development of inflammation and allergies. They also contribute to the development of cardiovascular diseases including thrombosis and arthrosclerosis. For example, by secreting tissue-type plasminogen activator (tPA), mast cell can initiate fibrinolysis. The purpose of this study was to determine whether adenosine, a potent mast cell activator, can modulate mast cell fibrinolytic activity. HLMC cells (human mast cell line) were dispersed from macroscopically normal lung obtained within 1 h of resection for lung cancer. All patients gave written informed consent, and the study was approved by the Leicestershire Research Ethics Committee. We found that 100 μM adenosine (2h at 37C) significantly increased mast cell tPA activity (by 58.6±3.5% for HMC-1 and 55±6.8% for HLMC) and tPA transcript expression level (by 6.4 folds for HMC-1 and 3.6 folds for HLMC). Adenosine deaminase abolished this potentiation. Real-time PCR revealed that HMC-1 predominantly expressed A2A and A2B receptors while HLMC abundantly expressed A2A, A2B and A3 subtypes. ZM241385 (1 μM), an A2A antagonist, significantly reduced adenosine induced mast cell tPA activity potentiation by 86.2% in HMC-1 (65% in HLMC); an inhibition similar (87.4% in HMC-1) to which obtained with a cocktail of antagonists for A1, A2A, A2B and A3 receptors (each at 1 μM). We also assessed mast cells fibrinolytic properties using a clot lysis assay (measuring fibrin clot lysis 10 hours after the full formation of a tissue factor-induced fibrin clot). Supernatants of HMC-1 treated for 24h with adenosine (100 μM) significantly increased clot lysis by 92.6%. This effect was abolished by ZM241385. In conclusion, our results show that adenosine potentiates mast cell fibrinolytic activity mainly through the A2A adenosine receptor.