Dias Lourdes, Rodrigues Mariana A P, Inoue Bruna R, Rodrigues Renata L, Rennó André L, de Souza Valéria B, Torres-Huaco Frank D, Sousa Norma C, Stroka Alessandra, Melgarejo Anibal R, Hyslop Stephen
Departamento de Farmacologia, Faculdade de Ciências Médicas, Universidade Estadual de Campinas (UNICAMP), Rua Tessália Vieira de Camargo, 126, Cidade Universitária Zeferino Vaz, 13083-887, Campinas, SP, Brazil.
Setor de Biologia, Divisão de Zoologia Médica, Instituto Vital Brazil, Niterói, RJ, Brazil.
Toxicon. 2016 Dec 1;123:25-44. doi: 10.1016/j.toxicon.2016.10.002. Epub 2016 Oct 5.
In this work, we examined some mechanisms involved in the hypotension caused by Lachesis muta (South American bushmaster) venom in anesthetized rats. Venom (1.5 mg/kg, i.v.) caused immediate hypotension that was maximal after 5 min and gradually returned to baseline over 60 min. Pretreatment of rats with the non-selective nitric oxide synthase (NOS) inhibitor N-nitro-L-arginine methyl ester (L-NAME) did not attenuate the early phase of venom-induced hypotension, but abolished the recovery phase and resulted in rapid death; a similar effect was observed with the soluble guanylate cyclase (sGC) inhibitor ODQ. In contrast, the hemodynamic responses to venom were not attenuated by the non-selective NOS inhibitor N-monomethyl-L-arginine, the inducible NOS inhibitor aminoguanidine, the phosphodiesterase 5 inhibitor sildenafil, the adenylate cyclase (AC) inhibitor SQ-22.536, the non-selective muscarinic receptor antagonist atropine, the bradykinin B2 receptor antagonist HOE-140 and the non-selective cyclooxygenase inhibitor indomethacin. Preincubation of venom with the PLA inhibitor pBPB had no effect on the immediate hypotension but tended to improve the recovery phase. Neither AEBSF (a serine proteinase inhibitor) nor EDTA (a metalloproteinase inhibitor) prevented the venom-induced hypotension, but AEBSF and not EDTA protected against the lethality of a high dose (3.0 mg/kg, i.v.). There were no marked changes in the ECG parameters with the various treatments, except with L-NAME and ODQ that increased the RR interval. Pulmonary thrombus formation was markedly enhanced by L-NAME and ODQ, and to a lesser extent by pBPB, especially in small vessels, whereas AEBSF and EDTA inhibited thrombus formation. Venom relaxed phenylephrine-precontracted thoracic aorta and pulmonary artery in vitro, with the latter being more sensitive. The relaxation was endothelium-dependent and was inhibited by ODQ but not by H-89, a protein kinase A (PKA) inhibitor. Together, these findings indicate involvement of the NO/sGC/cGMP, but not the AC/cAMP/PKA signaling pathway, in the hemodynamic responses to L. muta venom in rats. Muscarinic mechanisms, kinins and arachidonic acid metabolites are apparently not involved.
在本研究中，我们研究了南美巨蝮蛇毒导致麻醉大鼠低血压的一些机制。静脉注射蛇毒（1.5mg/kg）可立即引起低血压，5分钟时降至最低，60分钟内逐渐恢复至基线水平。用非选择性一氧化氮合酶（NOS）抑制剂N-硝基-L-精氨酸甲酯（L-NAME）预处理大鼠，并未减弱蛇毒诱导低血压的早期阶段，但消除了恢复阶段，并导致快速死亡；可溶性鸟苷酸环化酶（sGC）抑制剂ODQ也观察到类似效果。相反，非选择性NOS抑制剂N-甲基-L-精氨酸、诱导型NOS抑制剂氨基胍、磷酸二酯酶5抑制剂西地那非、腺苷酸环化酶（AC）抑制剂SQ-22.536、非选择性毒蕈碱受体拮抗剂阿托品、缓激肽B2受体拮抗剂HOE-140和非选择性环氧化酶抑制剂吲哚美辛，均未减弱对蛇毒的血流动力学反应。用磷脂酶A（PLA）抑制剂pBPB预孵育蛇毒，对即刻低血压无影响，但倾向于改善恢复阶段。AEBSF（一种丝氨酸蛋白酶抑制剂）和EDTA（一种金属蛋白酶抑制剂）均不能预防蛇毒诱导的低血压，但AEBSF而非EDTA可保护大鼠免受高剂量（3.0mg/kg，静脉注射）蛇毒致死。除L-NAME和ODQ使RR间期延长外，各种处理对心电图参数均无明显影响。L-NAME和ODQ显著增强肺血栓形成，pBPB在较小程度上也有增强作用，尤其是在小血管中，而AEBSF和EDTA抑制血栓形成。蛇毒在体外可使去氧肾上腺素预收缩的胸主动脉和肺动脉舒张，后者更敏感。这种舒张依赖于内皮，且被ODQ抑制，但不被蛋白激酶A（PKA）抑制剂H-89抑制。总之，这些结果表明，NO/sGC/cGMP信号通路参与了大鼠对南美巨蝮蛇毒的血流动力学反应，而AC/cAMP/PKA信号通路未参与。毒蕈碱机制、激肽和花生四烯酸代谢产物显然未参与。
