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|Type:||Artigo de periódico|
|Title:||Inflammatory Oedema Induced By The Lys-49 Phospholipase A2 Homologue Piratoxin-i In The Rat And Rabbit. Effect Of Polyanions And P-bromophenacyl Bromide|
De Castro R.C.
De Nucci G.
|Abstract:||Piratoxin-I (PrTX-I) is a Lys-49 phospholipase (PLA2) homologue, isolated from Bothrops pirajai snake venom, that has no phospholipase activity. In this study, we investigated the in vivo oedematogenic activity of PrTX-I in both the rat and the rabbit as well as the ability of PrTX-I to activate rat mast cells in vitro. In the rat paw and skin, PrTX-I (3-100 μg/paw) induced a dose-dependent oedema that was associated with extensive mast cell degranulation. The involvement of mast cells in PrTX-I-mediated oedema formation in the rat was further confirmed by the findings that this protein significantly activated rat peritoneal mast cells in vitro, causing the release of [14C]5-hydroxytryptamine ([14C]5-HT; 51 ± 1%). In the rabbit, PrTX-I (10-100 μg/site) also induced dose-dependent skin oedema formation that was not affected by either mepyramine (a histamine H1 receptor antagonist) or cyproheptadine (1.0 μg/site), indicating that mast cells do not play a role in this animal species. The bradykinin B2 receptor antagonist Hoe 140 (0.5 μg/site) and the platelet-activating factor (PAF) receptor antagonist WEB 2086 (200 μg/site) also failed to affect the PrTX-I-induced rabbit skin oedema, ruling out the involvement of kinins and PAF. The PLA2 inhibitor p-bromophenacyl bromide greatly reduced the PrTX-I-induced oedema in both the rat and the rabbit, and also inhibited the rat in vitro mast cell activation induced by this PLA2 homologue. The polyanions heparin and dermatan sulphate efficiently prevented oedema formation in both species, and heparin inhibited PrTX-I-induced rat mast cell degranulation. Our results are consistent with the suggestion that the cationic charge of PrTX-I plays a major role in the inflammatory responses induced by this PLA2 homologue. Copyright (C) 2000 Elsevier Science Inc.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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