IS DEFIBROTIDES ACTIVITY ON LEUKOCYTES ADENOSINE-RECEPTOR MEDIATED - AN IN-VITRO EX-VIVO APPRAISAL

Defibrotide both ''in vitro'' and ''ex vivo'' decreases PMN adhesion to nylon columns. This activity is blunted by 8-phenyltheophylline, a known blocker of adenosine A1/A2 receptors, suggesting that Defibrotide acts on that kind of receptors. Indomethacin, a blocker of PGI(2) synthesis, did not cancel DFT's activity, suggesting that PGI(2) is not involved in DFT's activity, at least under our experimental conditions. Non-PMN leukocytes behaved differently ''ex vivo'' than PMNs. DFT's activity was not blunted by 8-phenyltheophylline, suggesting that DFT acts on this kind of cell through a different mechanism. The ''in vitro'' experiment did not confirm ''ex vivo'' studies suggesting that in the ''in vitro'' experiment ''something'' is missing that is present in ''ex vivo'' experiments.