Effect of hsien-ho-t'sao (Agrimonia pilosa) on experimental thrombosis in mice.

The water extract of Hsien-Ho-T'sao (HHT) prolonged the tail bleeding time in conscious mice. This antihemostatic effect was dose-dependent and exhibited a biphasic pattern; i.e. its activity declined at doses higher than 0.5 mg/kg. the prolonged bleeding time persisted for at least 12 hr and maximal effect was observed at 3 hr after the oral administration of HHT 500 mg/kg. HHT was effective in preventing ADP-induced acute pulmonary thromboembolic death in mice, while aspirin and indomethacin had no effect on this model. HHT, like aspirin and indomethacin, also reduced the mortality in collagen- and sodium arachidonate-induced thromboembolic death. All three drugs caused no significant protection in endotoxin shock. HHT was found to suppress platelet aggregation markedly, but little effect on blood coagulation. In conclusion, HHT was proved to be effective in the treatment of acute pulmonary thromboembolism, and this effect was mainly due to its antiplatelet action.