Bothropstoxin-I and bothropstoxin-II are phospholipase A(2) homologues isolated from Bothrops jararacussu snake venom. The former is devoid of phospholipase A(2) activity whereas the latter has very low enzymatic activity. In this study, we have investigated the in vivo (rat paw and skin oedema) and...

Bothropstoxin-I and bothropstoxin-II are phospholipase A(2) homologues isolated from Bothrops jararacussu snake venom. The former is devoid of phospholipase A(2) activity whereas the latter has very low enzymatic activity. In this study, we have investigated the in vivo (rat paw and skin oedema) and in vitro (mast cell degranulation) inflammatory effects caused by bothropstoxin-I and bothropstoxin-II. Bothropstoxin-I (25-100 mu g/paw) and bothropstoxin-II (12.5-50 mu g/paw) caused dose-dependent rat paw oedema. The intradermal injection of bothropstoxin-I (0.125-5 mu g/site) and bothropstoxin-II (0.125-5 mu g/site) into rat skin also resulted in dose-dependent oedema formation. These oedematogenic activities were largely reduced in animals pretreated with the histamine/5-hydroxytryptamine (5-HT) receptor antagonist cyproheptadine (2 mg/kg, i.p. 0.5 h before). Similarly, p-bromophenacyl bromide, a compound known to inhibit phospholipase A(2) activity, significantly inhibited rat paw and skin oedema induced by both phospholipase A(2) homologues. The polyanion heparin (5 IU/site) significantly reduced the rat skin oedema induced by either bothropstoxin-I or bothropstoxin-II as well as the paw oedema (50 IU/site) induced by the former. When assayed in the rat peritoneal mast cells in vitro, both bothropstoxin-I (10 and 100 mu g/ml) and bothropstoxin-II (3 and 10 mu g/ml) significantly caused [C-14]5-HT release. The [C-14]5-HT release caused by these phospholipase A(2) homologues were reduced by p-bromophenacyl bromide and heparin (50 IU/ml). Our results indicate that oedema formation induced by bothropstoxin-I and bothropstoxin-II is mostly dependent on in vivo mast cell degranulation. Since heparin greatly reduced the oedematogenic activity of these phospholipase A(2) homologues, it is likely that the cationic charge of these substances plays a major role in the mast cell activation. Our results also indicate that p-bromophenacyl bromide may not be a suitable pharmacological tool to investigate the correlation between enzymatic activity and the inflammatory effects of phospholipases A(2)

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