LOW-DOSES OF ENDOTOXIN POTENTIATE VENOUS THROMBOSIS IN THE RABBIT

Procoagulant activity of the endothelium and of monocytes was induced by an intravenous administration of a low dose of endotoxin in the rab bit. Venous thrombosis induced by a 45-min stasis of the jugular vein was dramatically increased after the administration of endotoxin. Endo toxin enhanced venous thrombosis in a dose-dependent manner which was the highest after the administration of 1 mu g/kg. This effect increas ed with time but was optimal when endotoxin was injected 4 h before st asis induction. Leukocytes appear to play a key role in this process s ince mechlorethamine-induced leukopenia totally inhibited thrombus for mation. Hirudin and heparin, administered intravenously 5 min before s tasis, were both potent inhibitors of endotoxin-induced venous thrombo sis exhibiting ED(50) values of 3.8 +/- 1.0 and 2.3 +/- 1.1 mu g/kg, r espectively.