Abstract：
The plasma bacterial killing ability (BKA) is modulated by the stress response in vertebrates, including amphibians. The complement system is an effector mechanism comprised of a set of proteins present in the plasma that once activated can promote bacterial lysis. Herein, we investigated whether changes in plasma BKA as a result of the acute stress response and an immune challenge are mediated by the complement system in Rhinella diptycha toads. Additionally, we investigated whether the observed changes in plasma BKA are associated with changes in plasma corticosterone levels (CORT). We subjected adult male toads to a restraint or an immune challenge (with three concentrations of Aeromonas hydrophila heat inactivated), and then evaluated the plasma BKA against A. hydrophila, in vitro. We determined the complement system activity on plasma BKA, by treating the plasma (baseline, 1 h and 24 h post-restraint, and after the immune challenge) with ethylenediaminetetraacetic acid, heat, or protease. Our results showed increased CORT 1 h and 24 h after restraint and decreased plasma BKA 24 h post-restraint. The inhibitors of the complement system decreased the plasma BKA compared with untreated plasma at all times (baseline, 1 h, and 24 h after restraint), demonstrating that the plasma BKA activity is partially mediated by the complement system. The immune challenge increased CORT, with the highest values being observed in the highest bacterial concentration, compared with control. The plasma BKA was not affected by the immune challenge but was demonstrated to be partially mediated by the complement system. Our results demonstrated that restraint and the immune challenge activated the hypothalamus-pituitary-interrenal axis, by increasing plasma CORT levels in R. diptycha. Also, our results demonstrated the complement system is participative in the plasma BKA for baseline and post-stress situations in these toads.
摘要：
脊椎动物的应激反应调节了血浆细菌杀伤能力(BKA),包括两栖动物.补体系统是由血浆中存在的一组蛋白质组成的效应机制,所述蛋白质一旦被激活就可以促进细菌裂解。在这里，我们调查了二指蟾蜍急性应激反应和免疫攻击导致的血浆BKA变化是否由补体系统介导。此外,我们调查了观察到的血浆BKA变化是否与血浆皮质酮水平(CORT)的变化相关.我们对成年雄性蟾蜍进行抑制或免疫攻击（三种浓度的嗜水气单胞菌热灭活），然后评估血浆BKA对嗜水杆菌的影响，在体外。我们测定了血浆BKA的补体系统活性，通过处理血浆(基线，1小时和24小时后约束，免疫攻击后）用乙二胺四乙酸，热,或蛋白酶。我们的结果表明，抑制后1h和24hCORT升高，抑制后24h血浆BKA降低。与未处理的血浆相比，补体系统的抑制剂始终降低了血浆BKA（基线，1h,和约束后24小时)，证明血浆BKA活性部分由补体系统介导。免疫挑战增加了CORT，在最高的细菌浓度中观察到最高值，与对照相比。血浆BKA不受免疫攻击的影响，但已证明部分由补体系统介导。我们的结果表明，克制和免疫攻击激活下丘脑-垂体-肾间轴，通过增加R.diptycha的血浆CORT水平。此外，我们的结果表明,补体系统参与了这些蟾蜍基线和应激后的血浆BKA.
