Toxinological characterization of venom from Leptodeira annulata (Banded cat-eyed snake; Dipsadidae, Imantodini).

We investigated the histology of Duvernoy's venom gland and the biochemical and biological activities of Leptodeira annulata snake venom. The venom gland had a lobular organization, with secretory tubules formed by serous epithelial cells surrounding each lobular duct. The latter drained into a common lobular duct and subsequently into a central cistern. In contrast, the supralabial gland was mucous in nature. SDS-PAGE revealed a profile of venom components that differed from pitviper (Bothrops spp.) venoms. RP-HPLC also revealed greater complexity of this venom compared to Bothrops venoms. The venom had no esterase, l-amino acid oxidase or thrombin-like activity, but was proteolytic towards elastin-Congo red, fibrin, fibrinogen, gelatin and hide powder azure. The venom showed strong α-fibrinogenase and fibrinolytic activities and reduced the rate and extent of plasma recalcification. The proteolytic activity was inhibited by EDTA and 1,10-phenanthroline (metalloproteinase inhibitors) but not by AEBSF and PMSF (serine proteinase inhibitors). The venom had phospholipase A2 (PLA2) activity that was inhibited by varespladib. The venom cross-reacted with antivenoms to lancehead (Bothrops spp.), coralsnake (Micrurus spp.) and rattlesnake (Crotalus durissus terrificus) venoms. The venom did not aggregate rat platelets or inhibit collagen-induced aggregation, but partially inhibited thrombin-induced aggregation. The venom was hemorrhagic (inhibited by EDTA) and increased the vascular permeability (inhibited by varespladib) in rat dorsal skin. In gastrocnemius muscle, the venom caused myonecrosis and increased serum creatine kinase concentrations. In conclusion, L. annulata venom has various enzymatic and biological activities, with the local effects being mediated primarily by metalloproteinases and PLA2.

Hemodynamic responses to Lachesis muta (South American bushmaster) snake venom in anesthetized rats.

In this work, we examined the hemodynamic responses to Lachesis muta (South American bushmaster) venom in anesthetized male Wistar rats. Venom (1.5 mg/kg, i.v.) caused immediate hypotension that was followed by a gradual return towards baseline over 60 min; there were no significant changes in heart rate, ECG parameters and respiratory rate. A higher dose (3 mg/kg, i.v.) caused sustained hypotension, variable bradycardia, respiratory depression and fluctuations in ECG; death occurred within 10-60 min. Venom injected intramuscularly (15 mg/kg) produced a smaller decrease in blood pressure that was more persistent than with 1.5 mg/kg (i.v.). Pre-treatment with atenolol (selective ß1-adrenergic receptor antagonist) potentiated the response to venom (1.5 mg/kg, i.v.) and resulted in a hemodynamic profile similar to that seen with 3 mg/kg (i.v.). Macroscopically, systemic hemorrhage was seen only in the ileum, whereas histological analysis revealed extensive pulmonary hemorrhage; the heart, liver and kidney were generally unaffected. Intravascular pulmonary thrombosis occurred with venom given i.v. and i.m., but was less marked with the latter route. In rat isolated perfused hearts, venom caused a persistent decrease in left ventricular developed pressure but no change in heart rate, coronary flow or ECG; there was tissue necrosis and release of CK-MB that were abolished by pre-treating venom with the PLA2 inhibitor p-bromophenacyl bromide. These results show that in rats L. muta venom causes hypotension, bradycardia and respiratory depression, depending on the dose and route of administration. The hemodynamic responses apparently do not involve direct cardiotoxicity and are modulated by the adrenergic system.

Biological activities of a lectin from Bothrops jararacussu snake venom.

Snake venoms contain saccharide-binding lectins. In this work, we examined the biological activities of a lectin (BjcuL) purified from Bothrops jararacussu snake venom by chromatography on non-derivatized Sepharose 4B and Sephacryl S-200 HR. The protein, a homodimer with subunits of 14.5 kDa, gave a single immunoprecipitin line in immunoelectrophoresis and cross-reacted in ELISA with antivenoms raised against Bothrops spp. (lanceheads), Micrurus spp. (coral snakes), Crotalus durissus terrificus (South American rattlesnake), and arthropod (Loxosceles gaucho, Phoneutria nigriventer and Tityus serrulatus) venoms. BjcuL agglutinated human formaldehyde-fixed erythrocytes at > or = 100 ng/ml and was inhibited by lactose and EDTA (> or = 2 mM) and high concentrations (> 100 mM) of glucose and sucrose, but not by N-acetylglucosamine. BjcuL had no direct hemolytic activity and was devoid of esterase, PLA2 and proteolytic activities. The lectin (up to 200 microg/ml) did not aggregate human platelet-rich plasma (PRP) or washed platelets (WP), nor did it alter the aggregation induced by ADP in PRP or by thrombin in WP. When injected into mouse hind paws, BjcuL (10-100 microg/paw) caused edema and increased vascular permeability, with a maximum effect after 1h that persisted for up to 6 h (edema) or gradually decreased after the peak interval (vascular permeability). No hemorrhage was observed in BjcuL-injected paws. In anesthetized rats, B. jararacussu venom (200 microg/kg, i.v.) produced sustained hypotension (maximum decrease of approximately 60%) whereas a similar dose of BjcuL decreased the blood pressure by approximately 15%, with a rapid return to the resting level.