Inhibitory effect of TCV-309, a novel platelet activating factor (PAF) antagonist, on endotoxin-induced disseminated intravascular coagulation in rats: possible role of PAF in tissue factor generation.

The possible involvement of platelet activating factor (PAF) in the pathogenesis of endotoxin-induced disseminated intravascular coagulation (DIC) was investigated in rats using a novel potent PAF antagonist, TCV-309. TCV-309 (> 1 mg/kg, i.v.) showed beneficial effects in rats with experimental DIC induced by a 4-hour sustained infusion of endotoxin (1 mg/kg) in a dose-dependent manner. TCV-309 (1 mg/kg) significantly ameliorated the decrease in platelet count and plasma fibrinogen, the prolongation of prothrombin time (PT) and activated partial thromboplastin time (APTT) and the increase in fibrin and fibrinogen degradation products (FDP) and inhibited glomerular fibrin deposition. Furthermore, plasma tissue factor (TF) activity was greatly increased in the DIC rats, and this was also significantly decreased by TCV-309 (1 mg/kg). TCV-309 (1 mg/kg) did not affect these parameters in normal rats. A 4-hour sustained infusion of PAF (60 micrograms/kg) caused mild but significant changes in some DIC parameters such as PT, fibrinogen and FDP concentration and increased the plasma TF activity. TCV-309 (1 mg/kg) inhibited all these PAF-induced changes. TCV-309 (0.1 mM) itself had no direct in vitro effects on the blood coagulation system including TF activity. These results strongly suggest that PAF plays a role in the pathogenesis of endotoxin-induced DIC via the generation of TF. Prophylactic use of PAF antagonists may therefore be useful for the treatment of DIC with sepsis.