Synergistic effect of adenosine and 2-methylthio-ATP on vWF release. (A) Confluent HUVECs were incubated for 30 minutes at 37°C in the presence of ATP adenosine (Ado), and 2-methylthio-ATP (MeS) (all agonists tested at 100 μmol/L) in the presence or absence of 100 μmol/L IBMX. Results are the mean ± SEM of 5 experiments. Because of large variations in vWF release in this series, the results are shown as relative values, with release at 30 minutes from unstimulated cells defined as 100%. The effects of MeS and Ado alone were small, but the response to the combination of Mes + Ado was similar to or greater than the response to ATP. *P < .02v control (C) cells; **P < .02 v control cells and cells treated with Ado or MeS alone. (B) Adenosine-induced vWF release: dose-response in the presence of IBMX (100 μmol/L), MeS (100 μmol/L), and IBMX + MeS. Each combination was added to confluent HUVECs for 30 minutes at 37°C. Results are the mean ± SEM of 5 experiments. *P < .002 v control cells not stimulated with adenosine.