Rat blood leucocytes, unlike rabbit leucocytes, do not generate procoagulant activity on exposure to endotoxin.

We have investigated the ability of rat and rabbit leucocytes to generate procoagulant activity (PCA) in response to endotoxin in vitro and in vivo. On prolonged incubation with endotoxin (10 micrograms/ml f.c.) isolated rabbit leucocytes developed strong PCA as measured by clotting and amidolytic assay. In contrast, rat leucocytes failed to produce any PCA even in the presence of huge amounts of endotoxin (200 micrograms/mol f.c.). When rabbits were given two spaced endotoxin injections (25 micrograms/kg consistently showed marked PCA. Again, unlike in the rabbit, rat leucocytes obtained after 2 endotoxin injections (up to 2 mg/kg body wt) showed absolutely no PCA. These findings support the view that leucocytes are involved in endotoxin-induced disseminated intravascular coagulation (DIC) 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.