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ABSTRACT:Agkistrodon halys is one of several dangerous snake species in Iran. Among the most important signs and symptoms in patients envenomated by this snake is disseminated intravascular coagulation. A thrombin-like enzyme, called AH143, was isolated from Agkistrodon halys venom by gel filtration on a Sephadex G-50 column, ion-exchange chromatography on a DEAE-Sepharose and high performance liquid chromatography (HPLC) on a C18 column. In the final stage of purification, 0.82 mg of purified enzyme was obtained from 182.5 mg of venom. The purified enzyme showed a single protein band by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), under reducing conditions, and its molecular mass was found to be about 30 kDa. AH143 revealed clotting activity in human plasma, which was not inhibited by EDTA or heparin. This enzyme still demonstrated coagulation activity when exposed to variations in temperature and pH ranging, respectively, from 30 to 40°C and from 7.0 to 8.0. It also displayed proteolytic activities on synthetic substrate. The purified enzyme did not show any effect on casein. We concluded that the venom of the Iranian snake Agkistrodon halys contains about 0.45% single procoagulant protein which appears to be a thrombin-like enzyme.

Scorpion envenomation is a life-threatening condition, especially in children and elderly individuals affected by respiratory and cardiovascular diseases. In this study, the toxic effects of median lethal dose (LD50) injections of Mesobuthus eupeus (Me) venom on the heart and lungs of anesthetized rabbits were investigated. Six rabbits were selected and alterations in their electrocardiogram, heart rate, respiration and blood pressure before and after venom injection were recorded. Cardiac troponin T (cTnT), creatinine kinase muscle-brain fraction (CK-MB) and lactate dehydrogenase (LDH) were measured at 0, 1 and 3 hours after envenomation and pathology studies were carried out postmortem. All the animals showed signs and symptoms of envenomation within 40 minutes and died 3 to 3.5 hours after venom injection. Pathology studies revealed alveolar edema in 100% of the rabbits and myocardial infarction in 16%. The main histopathological changes were myocytolysis, coagulation necrosis, focal hemorrhage, thrombus formation both in myocardium and on endocardial surfaces as well as inflammatory infiltrates in the heart and hemorrhage, vascular thrombus and interstitial inflammation in the lungs. ECG monitoring of rabbits showed ST elevation, ST depression and inverted T and Q waves. In addition, although cTnT levels increased in 16% of the animals and serum LDH was also augmented, none of these changes was statistically significant. The enzyme CK-MB also did not show any change after Me venom injection. In conclusion, the results of this study showed that Me venom killed animals in less than 3.5 hours through severe pulmonary damage and it appears that the deaths could not be attributed to cardiovascular lesions. Therefore, Me venom effects on the lungs are so important that they appear to be independent of heart damage.

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An anticoagulant factor was purified from the venom of the Iranian snake Agkistrodon halys by gel filtration on Sephadex G-50 and ion-exchange chromatography on DEAE-Sepharose. In the final stage of purification, the percentage recovery of purified anticoagulant factor was found to be 83%. The purified anticoagulant factor revealed a single protein band in SDS-polyacrylamide electrophoresis under reducing conditions and its molecular weight was about 22 kDa. The purified peptide did not show any effect on casein, BApNA or plasma.