Proteinase inhibitors from plants represent a form of storage protein or may be involved in plant defense mechanisms against pests and diseases. In this study, we have investigated the oedematogenic activity of DMTI (20 kDa) and DMTI-II (23 kDa), two serine proteinases inhibitors isolated from Dimorphandra mollis (Leguminosae-Mimosoideae) seeds, belonging to the Kunitz family. Paw oedema was induced in male Wistar rats, and measured before and selected times after injection of the proteinase inhibitors. Injection of DMTI-II (3-100 mu g/paw) induced a dose-dependent rat paw oedema of rapid onset and short duration, whereas DMTI (3-100 mu g/paw) caused a discrete response. The histamine/5-HT receptor antagonist cyproheptadine (2 mg/kg) markedly reduced the DMTI-II-induced oedema. The bradykinin 132 receptor antagonist JE 049 (0.6 mg/kg), the tachykinin NK1 receptor antagonist SR140333 (100 mu g/kg) or the NK2 receptor antagonist SR48968 (1 mg/kg) all significantly reduced the DMTI-II-induced oedema. Depletion of sensory neuropeptides by capsaicin also resulted in a significant reduction of oedema formation. In rat isolated peritoneal mast cells, DMTI-II failed to directly release histamine. In conclusion, the proteinase inhibitor DMTI-II induces rat paw oedema by triggering the formation of different inflammatory mediators and pathways, where mast cells and sensory fibers seem to play a pivotal role. (c) 2005 Published by Elsevier Ltd.472150155