Inhibition of plasma kallikrein. Kininase and kinin-like activities of preparations from the medicinal leeches.

The medicinal leech salivary gland secretion deprived of hirudin antithrombin activity inhibits amidolytic (substrate S-2302) and kininogenase (substrate kininogen) activities of plasma kallikrein, the main component of the intrinsic mechanism of blood coagulation. It therefore possesses high anticoagulant properties. Kininase (substrate bradykinin) activity of leech saliva and extracts from the medicinal leeches, as well as kinin-like effects of extracts heated at 100 degrees C have been detected. The last one is correlated with the hyperalgetic property of the heated extract. An analgetic effect was observed with the unheated extract but not with leech saliva after intranasal administration to rats.