Teixeira A L, Fontoura B F, Freire-Maia L, Machado C R, Camargos E R, Teixeira M M
Departamento de Morfologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antonio Carlos, 6627, Pampulha, 31270 901 Belo Horizonte, Minas Gerais, Brazil.
Toxicon. 2001 May;39(5):703-9. doi: 10.1016/s0041-0101(00)00200-2.
The ability of toxins to activate the cardiovascular system plays an important role in the morbidity and lethality of the Tityus serrulatus scorpion envenoming. Most of the actions of the scorpion toxins are indirect and due to the release of adrenergic and cholinergic neurotransmitters. Accordingly, treatment following envenoming is targeted towards inhibition of adrenergic and cholinergic receptors. Here, we have sought evidence for a direct action of T. serrulatus venom on the isolated rat heart (Langendorff's method). We show that the bradycardia induced by T. serrulatus venom was completely blocked by atropine, a muscarinic receptor antagonist. Similarly, the increase in heart rate that follows the venom-induced bradycardia was totally inhibited by a beta(1)-adrenoceptor antagonist or by chemical sympathetic denervation with 6-hydroxydopamine. In contrast to these findings, the venom-induced increase in contractile force was not modified by beta(1)-adrenoceptor blockade or by chemical sympathetic denervation. The results clearly demonstrate that the chronotropic effects of T. serrulatus are dependent on neurotransmitter release, but the inotropic effects are not. The neurotransmitter-independent increase in contractility seems to be a direct action of the venom on cardiomyocytes. We suggest that this direct effect on cardiac fibers may play a role in the development of cardiac arrhythmias and contractility defects following envenoming with T. serrulatus scorpion.
毒素激活心血管系统的能力在巴西金幽灵蝎蜇伤的发病率和致死率中起着重要作用。蝎毒素的大多数作用是间接的，归因于肾上腺素能和胆碱能神经递质的释放。因此，蜇伤后的治疗旨在抑制肾上腺素能和胆碱能受体。在此，我们寻找了巴西金幽灵蝎毒液对离体大鼠心脏（Langendorff法）直接作用的证据。我们发现，巴西金幽灵蝎毒液诱导的心动过缓被毒蕈碱受体拮抗剂阿托品完全阻断。同样，毒液诱导的心动过缓后出现的心率增加被β1肾上腺素能受体拮抗剂或用6-羟基多巴胺进行化学性交感神经去支配完全抑制。与这些发现相反，毒液诱导的收缩力增加并未因β1肾上腺素能受体阻断或化学性交感神经去支配而改变。结果清楚地表明，巴西金幽灵蝎的变时作用依赖于神经递质释放，但变力作用并非如此。与神经递质无关的收缩力增加似乎是毒液对心肌细胞的直接作用。我们认为，这种对心脏纤维的直接作用可能在巴西金幽灵蝎蜇伤后心律失常和收缩力缺陷的发生中起作用。
