Role of leucocyte procoagulant activity in endotoxin-induced DIC: Evidence from comparative studies in rats and rabbits

We have investigated the ability of rat and rabbit leucocytes to generate coagulant activity (PCA) in response to endotoxin in vitro and in vivo. On prolonged incubation with endotoxin (10 μg/ml f.c.) isolated rabbit leucocytes developed strong PCA as measured by clotting and amidolytic assay. In constrast, rat leucocytes failed to produce any PCA even in the presence of huge amounts of endotoxin (200 μg/ml f.c.). When rabbits were given two spaced endotoxin injections (25 μg/kg b.w., 24 h apart) blood leucocytes harvested 30-60 min after the second injection consistently showed marked PCA. Again, unlike the rabbit, rat leucocytes obtained after two endotoxin injections (up 2 mg/kg b.w.) were completely devoid of PCA. These findings support the view that leucocytes are involved in endotoxin-induced disseminated intravascular coagulation in rabbits. On the other hand the poor response of rat leucocytes to endotoxin might help explain the resistance of rats to DIC and Sanarelli-Shwartzman reaction.