Hematological, hemostatic and clinical chemistry disturbances induced by Crotalus durissus terrificus snake venom in dogs.

The aim of this study was to investigate the hematological, hemostatic and biochemical disturbances induced by the injection of Crotalus durissus terrificus venom in dogs under controlled conditions. For this purpose three groups of animals were used: an experimental group (E), which was injected i.m. with C. durissus terrificus venom (1 mg/kg); and two control groups--antivenom (AV) and control (C)--which were injected i.m. with 150 mM NaCl. Groups E and AV were treated i.v. with Crotalus antivenom 2 hours after the first injection. Serum levels of alkaline phosphatase and alanine aminotransferase were increased in groups E and AV at 24 and 48 hours after serumtherapy, respectively. The increased serum levels of myoglobin, creatine kinase and aspartate aminotransferase demonstrated that animals developed rhabdomyolysis. A persistent neutrophilic leukocytosis was already noticeable at 2 hours after envenomation and lasted even after serumtherapy. The animals of groups E and AV presented eosinopenia 24 hours after serumtherapy, and collagen-induced platelet hypoaggregation was observed without thrombocytopenia. Increased levels of fibrinogen/fibrin degradation products (FnDP/FgDP), hypofibrinogenemia, and alpha2-antiplasmin consumption were observed at 2 hours after envenomation, indicating secondary activation of fibrinolysis. Our data suggest that the biochemical and hemostatic disturbances induced by C. durissus terrificus venom in dogs are related to its myotoxic and thrombin-like activities.

Contribution of crotoxin for the inhibitory effect of Crotalus durissus terrificus snake venom on macrophage function.

Previous work of our group demonstrated that Crotalus durissus terrificus venom has a dual effect on macrophage function: it inhibits spreading and phagocytosis and stimulates hydrogen peroxide and nitric oxide production, antimicrobial activity and glucose and glutamine metabolism of these cells. Crotalid venom also induces analgesia and this effect is mediated by opioid receptors. The involvement of opioidergic mechanism and the determination of the active component responsible for the inhibitory effect of crotalid venom on macrophage function were investigated. The venom reduced the spreading and phagocytic activities of peritoneal macrophages. This effect was observed in vitro, 2 h after incubation of resident peritoneal macrophages with the venom, and in vivo, 2 h after subcutaneous injection of the venom. The inhibition of phagocytosis was not modified by naloxone, an antagonist of opioid receptors. Venom neutralization with crotalid antivenom abolished the inhibitory effect of the venom, indicating that venom toxins are involved in this effect. Crotoxin, the main toxin of crotalid venom, s.c. injected to rats or added to the medium of peritoneal cell incubation, inhibited macrophage function in a similar manner to that observed for crude venom. The present results suggest that crotoxin causes a direct inhibition of macrophage spreading and phagocytic activities and may contribute to the inhibitory effect of crotalid venom on macrophage function.

Biological and immunochemical characterization of Micrurus altirostris venom and serum neutralization of its toxic activities.

Micrurus altirostris venom from Rio Grande do Sul State, Brazil, was characterized by its biological activities, immunochemical properties and electrophoretic pattern. The results showed a high edematogenic activity, whose peak was observed after 30min of venom injection, as well as a high indirect hemolytic activity. This venom was myotoxic, as shown by a peak of CK release at 6h after injection, and also by the appearance of muscular lesions characterized by necrosis, loss of striated muscle fibers, and the presence of vacuolization, edema and inflammatory infiltrate. This venom showed minimum proteolytic activity and no hemorrhagic, dermonecrotic or coagulant activities. Nonetheless, M. altirostris venom presented high lethal activity. Electrophoretic patterns of Micrurus frontalis and M. altirostris venoms showed different protein bands. Anti-elapidic serum could recognize M. frontalis (homologous) and M. altirostris (heterologous) venoms by Western blotting, and both venoms presented similar titers when assayed by ELISA. The results observed on neutralization tests showed that the anti-elapidic serum produced by Instituto Butantan neutralized myotoxic and hemolytic activities. However, this antivenom could not neutralize the lethal activity of M. altirostris venom. Thus, these data suggest that M. altirostris venom presents different biological, enzymatic and immunological characteristics from other Micrurus venoms, and some activities are not neutralized by the commercial anti-elapidic serum produced in Brazil.