Ação dos venenos das espécies de sapos Rhaebo guttatus e Rhinnela marina em aorta de ratos Wistar

Abstract

The species of toad Rhaebo guttatus and Rhinella marina are widely found in Brazilian Amazonia, and, in accordance with what has already been described in the literature, their venoms are rich in bufadienolides, cardiac glycosides that act in Na+/K+ATPase. This study aimed to evaluate the influence of these compounds on the vascular reactivity in isolated aorta rings from Wistar rats, as well as to evaluate their effects in the Na+/K+ATPase activity. Aortic segments with and without endothelium were set up in an organ bath containing Krebs-Henseleit solution and concentration-response curves to contractile or relaxing agonists were performed in the presence or the absence of different concentrations of the studied venoms. The R. guttatus venom showed anti contractile and relaxing effects, both of them independent from the endothelium. The R. marina venom did not present anti contractile effect, however it increased the percentage of the endothelium dependent relaxation. There was an increase of the endothelial Na+ /K+ ATPase activity in segments that were previously incubated with the concentration 0.7 µg/mL of the R.guttatus venom. Cell viability tests were made in order to evaluate the cytotoxicity of the studied venoms. None of both venoms concentration used in this work caused cell death in splenocytes from Wistar rats. Although the mecanisms by which the analyzed venoms lead to the observed effects were not investigated, we suggest that they occour due to the activation of unusual Na+ /K+ ATPase pathways, that result in the increased production of nitric oxide, or in the decrease of calcium inflow, as well as in the reduction of the contractile proteins afinity by this ion. Besides this, it is possible that some compounds that were not identified yet may be associated to the observed effects. Thus, we showed that R. guttatus and R. marina venoms have important action in blood vessels, and they may have powerful substance that can be used in the arterial hypertension treatment.