The effects of Gaboon viper (Bitis gabonica) venom on the electrical and mechanical activity of the guinea-pig myocardium

Cardiotoxic effects of the Vipera ammodytes ammodytes venom fractions in the isolated perfused rat heart

The nose-horned viper (Vipera ammodytes ammodytes) is the most venomous European snake. Its venom is known as haematotoxic, myotoxic and neurotoxic but it exerts also cardiotoxic effects. To further explore the cardiotoxicity of the venom we separated it into four fractions by gel filtration chromatography. Three fractions that contain polypeptides (A, B, and C) were tested for their effects on isolated rat heart. Heart rate (HR), incidence of arrhythmias (atrioventricular (AV) blocks, ventricular tachycardia, ventricular fibrillation, and asystolia), coronary flow (CF), systolic, developed and diastolic left ventricular pressure (LVP) were measured before, during, and after the application of venom fractions in three different concentrations. Fraction A, containing proteins of 60-100 kDa, displayed no effect on the rat heart. Fractions B and C disturbed heart functioning in similar way, but with different potency that was higher by the latter. This was manifested by significant decrease of HR and CF, the increase of diastolic, and the decrease of systolic and developed LVPs. All hearts treated with fraction C in the final CF concentrations 22.5 and 37.5 μg/mL suffered rapid and irreversible asystolia without AV blockade. They underwent also ventricular fibrillation and ventricular tachycardia. Fraction B affected hearts only at the highest dose inducing asystolia in all hearts, ventricular fibrillation in 80% and ventricular tachycardia in 70% of the hearts. Venom fraction C induced 71% of all recorded heart rhythm disturbances, significantly more than fraction B, which induced 29%. Most abundant proteins in fraction C were secreted phospholipases A₂ among which the venom component acting on the heart is most probably to be looked for.

Infant death after nose-horned viper (Vipera ammodytes ammodytes) bite in Croatia: A case report

A case of a 45-day-old male infant, bitten on the neck by nose-horned viper (Vipera ammodytes ammodytes), is reported. This episode occurred while the baby was on a picnic with his parents in a hill near a town in southern Croatia. In spite of immediate arrival at hospital, where antivenom was administrated and all the necessary treatment measures were carried out, the infant died 6 h following the bite. The cause of death was severe and progressive hyperkalaemia, massive intravascular haemolysis, severe coagulopathy and myocardial dysfunction.

Dose dependent effects of standardized nose-horned viper (Vipera ammodytes ammodytes) venom on parameters of cardiac function in isolated rat heart

Direct, dose dependent effects of the nose-horned vipers (Vipera ammodytes ammodytes) venom on various parameters of cardiac action in isolated rat hearts were examined. Biochemical (protein content, SDS polyacrylamide gel electrophoresis) and biological (minimum haemorrhagic and necrotizing dose and lethal dose (LD(50))) characterization of the venom was performed before testing. The hearts were infused with venom doses of 30, 90 and 150 microg/mL for 10 min followed by 30 min of wash out period. Left ventricular pressure, coronary flow, heart rate, atrioventricular conduction, myocardial oxygen consumption, incidence and duration of arrhythmias were measured and relative cardiac efficiency was calculated. Cardiac CPK, LDH, AST and troponin I were measured as biochemical markers of myocardial damage. The venom caused dose dependent electrophysiological instability and depression of contractility and coronary flow. Effects on the heart rate were biphasic; transient increase followed by significant slowing of the frequency. Relative cardiac efficiency decreased as oxygen consumption remained high relative to the heart rate-contractility product, indicating purposeless expenditure of oxygen and energy. Effects by the dose of 30 microg/mL were highly reversible while the dose of 90 mug/mL caused damages that were mostly irreversible. The dose of 150 mug/mL induced irreversible asystolic cardiac arrest.

The Gaboon viper, Bitis gabonica: hemorrhagic, metabolic, cardiovascular and clinical effects of the venom

The effects of Bitis gabonica venom have been studied in several animal species, including the monkey, dog, rabbit, rat and guinea pig. Further information has been provided by observations on the effects of snake bite in man. Bitis gabonica venom exerts a number of cytotoxic and cardiovascular effects: cytotoxic effects include widespread hemorrhage, caused by the presence of two hemorrhagic proteins. These hemorrhagins bring about separation of vascular endothelial cells and extravasation of blood into the tissue spaces. Metabolic alterations include decreased oxygen utilization by tissues and increased plasma glucose and lactate concentrations. Metabolic non-compensated acidosis has also been seen in the rat as a consequence of the cytotoxicity of the venom. Cardiovascular effects include disturbances in atrio-ventricular conduction and reduction in amplitude and duration of the action potential brought about by a decreased calcium membrane conductance. A progressive decrease in myocardial contractility can also be attributed to the decreased calcium conductance, which together with the severe acidosis may cause death in experimental animals. A severe, though reversible, vasodilatation was observed after envenomation due to unidentified compounds in the venom. In man, envenomation causes a variable clinical picture depending on the time course and severity of envenomation. Frequently seen effects include hypotension, hemorrhage at the site of the bite and elsewhere and disseminated intravascular coagulation. Envenomation can be satisfactorily treated with antivenom.

The mechanical and electrical effects of rhinoceros viper (Bitis nasicornis) venom on the isolated perfused guinea pig heart and atrial preparations

The mechanical and electrical effects of the venom of Bitis nasicornis were studied on the guinea-pig Langendorff and left atrial myocardium preparations. While Langendorff preparations were treated with individual doses of 0.1, 0.6 and 1.4 mg, isolated left atria were treated using concentrations of 2.0, 20 and 200 micrograms/ml of venom in the perfusion solution. In the Langendorff preparation, transient increases in left ventricular systolic pressure (LVSP) and heart rate (HR) were seen after 0.1 mg of venom. When 0.6 mg of venom was given, the increases were followed by decreases, while 1.4 mg doses simply induced decreases in LVSP and HR. After both 0.6 and 1.4 mg doses the decreases were accompanied by increases in left ventricular diastolic pressure. In addition to these mechanical effects, transient increases in HR with atrio-ventricular blocks, ventricular extrasystoles and tachycardia were observed after each dose. In the left atrium the 2 micrograms/ml venom concentration produced an increase, followed by a decrease, in the maximum tension developed, which was only seen to decrease with higher concentrations of 20 and 200 micrograms/ml of venom. A dose dependent significant reduction in the action potential duration was observed for the doses of 0.6 and 1.4 mg in the ventricle and for all three concentrations in the atrium.

Acidotic effect of gaboon viper (Bitis gabonica) venom in the urethane-anaesthetized rat

1. Intravenous venom (4 mg/kg) caused a non-compensated metabolic acidosis. 2. Bicarbonate concentration, base excess, standard base excess and pH all fell dramatically. 3. A respiratory impairment occurred characterized by pulmonary oedema and a fall in arterial pO2. 4. Acidosis occurred soon after venom when pO2 was still normal, indicating that changes in tissue metabolism contributed to the acidosis independently of reduced oxygen availability.

Acid-base, plasma lactate and glucose changes in the rabbit following administration of Gaboon viper (Bitis gabonica) venom

The acid-base and metabolic effects of Bitis gabonica venom administered intravenously to the anaesthetised rabbit were studied. Doubling doses of venom from 0.125 mg/kg to 1.0 mg/kg were used. Venom caused progressive and significant increases in plasma glucose and plasma lactate levels although oxygen consumption only became significantly lower after the fourth dose. Standard base excess (SBE) became significantly more negative after the third dose of venom and the fall in pH became significant at the same point. The results indicate that venom induces a metabolic acidosis in the rabbit and because the acidosis occurs in the absence of any fall in arterial PO2, it cannot be considered a consequence of impaired pulmonary ventilation. The reduction in oxygen uptake is likely to occur at a cellular level with a shift from aerobic to anaerobic metabolism hence the increase in plasma lactate levels. However, the magnitude of the acidosis is unlikely to be the principal cause of death under experimental conditions.

The effects of gaboon viper (Bitis gabonica) venom on voltage-clamped single heart cells

The effects of crude B. gabonica venom on single ventricular myocytes from guinea-pig hearts were studied using the patch clamp technique in the 'whole cell' mode. Irreversible effects on the membrane currents, which became prominent within 15 min of venom application, were: (1) a decrease in the time invariant current (associated with the inward rectifying K+ current), most clearly seen over a voltage range negative to the resting membrane potential; and (2) a decrease in the peak inward current (associated with the Ca2+ current) elicited by steplike depolarizations from a holding potential of -40 mV. A transient increase in the peak inward current, which preceded its eventual decline, was also noticed; it peaked 6-10 min after the venom was applied. Application of the venom to unclamped, stimulated cells resulted in a shortening of the plateau phase and disturbances of the repolarization phase of action potentials. An early transient prolongation and elevation of the plateau was observed, occurring with the same time course of the transient increase in the peak inward current. No signs of damage to the cell membrane integrity, neither electrical (appearance of a leakage current) nor morphological (surface blebs, loss of striation pattern and of rodlike shape in the isolated myocytes), accompanied the effects observed on ionic currents and action potential activity, supporting the hypothesis of a selective cardiotoxic action of B. gabonica venom.