Pharmacological study of edema and myonecrosis in mice induced by venom of the bushmaster snake (Lachesis muta muta) and its basic Asp49 phospholipase A(2) (LmTX-I).

Previous in vitro studies show that Lachesis muta venom and its purified Asp49 phospholipase A(2), named as LmTX-I, display potent neurotoxic and myotoxic activities. Here, an in vivo study was conducted to investigate some pharmacological effects of the venom or its LmTX-I toxin, after intra-muscular injection in tibialis anterior (TA) and following subplantar injection in hind paws of mice. Findings showed that LmTX-I increased plasma creatine kinase activity and produced strong myonecrosis and inflammatory reactions in TA muscle. In addition to these effects, the venom also induced intense local hemorrhage. Pre-treatment of the venom with EDTA (5 mM) significantly inhibited the edema and hemorrhage. Histological examination showed that L. muta venom caused inner dermal layer thickening in the pad hind paw. In addition, there was marked inflammatory cell infiltration, particularly of neutrophils, and hemorrhage. LmTX-I also demonstrated edema-forming activity, which was inhibited by pretreatment with indomethacin.