Characterization and mechanisms of the cardiovascular and haemodynamic alterations induced by scorpion venom in rats

The scope of this work was to investigate the nature, chronology and mechan isms of the cardiovascular disorders induced by scorpion envenomation. Anae sthetized rats were instrumented for measurement of cardiac output (CO), re nal (RBF) and muscular (HBF) blood flows (pulsed Doppler flowmetry), blood pressure, heart rate and dP/dt. Buthus occitanus venom (BO) was administere d intravenously in the absence/presence of different pre-treatments. BO dos e-dependently (150-300 mu g/kg) increased blood pressure, dP/dt, total peri pheral (TPR), renal (RVR) and muscular (HVR) vascular resistances, and decr eased CO, RBF and HBF. Recovery occurred after 150 but not after. 300 mu g/ kg. BO, 600 mu g/kg, produced qualitatively similar effects but arrhythmias developed and mortality increased. Pre-treatment with phentolamine prevent ed the rises in TPR, RVR, HVR and blood pressure and the decreases in CO, R BF and HBF induced by BO, 300 mu g/kg. Pre-treatment with propranolol preve nted the rise in dP/dt and the occurrence of arrhythmias and limited the ri se in RVR and the drop in RBF induced by BO, 300 mu g/kg. Phentolamine, pro pranolol and their combination also prevented BO, 600 mu g/kg-induced morta lity. Other pre-treatments (bosentan, losartan, diltiazem, mepyramine) were almost ineffective vs. BO effects. Finally, BO, 300 mu g/kg, induced a 30- 40-fold increase in plasma epinephrine and norepinephrine levels, but no ch ange in plasma endothelin-l levels. Thus in anaesthetized rats, the pattern of the cardiac and systemic and regional haemodynamic effects of BO is typ ically that of and results From catecholamine outpouring-induced alpha- and beta-adrenoceptor stimulation. (C) 2000 Editions scientifiques et medicale s Elsevier SAS.