Moretti Eduardo Hermógenes, Ortega Chinchilla Jesús Eduardo, Marques Fernando Silveira, Fernandes Pedro Augusto C M, Gomes Fernando Ribeiro
Department of Physiology, Institute of Bioscience, University of São Paulo, 05508-900 São Paulo, Brazil.
Department of Physiology, Institute of Bioscience, University of São Paulo, 05508-900 São Paulo, Brazil.
Physiol Behav. 2018 Jul 1;191:73-81. doi: 10.1016/j.physbeh.2018.04.008. Epub 2018 Apr 9.
Ectothermic vertebrates develop behavioral fever in response to bacterial products, with potential corresponding metabolic costs associated with immune stimulation. Although behavioral fever has been described in several taxa under laboratory conditions, some important questions regarding metabolic response to bacterial products at different temperatures and effectiveness of behavioral fever remain open. Many ectotherms, such as nocturnal anurans, may be active in the field at environmental conditions that restrict thermoregulation during the immune response. How does the metabolic response to bacterial products under ecologically relevant but unfavorable thermal field conditions compare to that measured in fever thermal preferendum? Additionally, are there differences in the partitioning of metabolic costs associated with immune stimulation and Arrhenius effect (biochemical reactions rate) at normal versus fever thermal preferendum? We compared the energy expenditure untreated and LPS-treated yellow Cururu toads (Rhinella icterica) at temperature corresponding to field activity during winter nights, and at normal and fever thermal preferendum. It was hypothesized that the metabolic response to LPS would be proportionally lower at higher body temperatures. To test these hypotheses, we measured temperature in the field during night using agar models, as well as normal and fever thermal preferendum of the toads within a thermal gradient. Subsequently, we measured the toad's metabolic rates at mean agar models temperature, as well as at normal and fever thermal preferendum. Lastly, we calculated the Metabolic response to LPS as the ratio between MR/MR in each of these mean temperatures. Our results show that metabolic rates do not increase in response to LPS at the agar models temperature typical of the winter nights under which theses toads maintain reproductive activity. Moreover, LPS treatment increased the metabolic costs relative to Arrhenius effects at normal thermal preferendum but not at fever thermal preferendum. In this way, metabolic response to LPS was comparative lower at fever than normal thermal preferendum in yellow Cururu toads.
变温脊椎动物会因细菌产物而产生行为性发热，同时免疫刺激可能会带来相应的代谢成本。尽管在实验室条件下已经在几个分类群中描述了行为性发热，但关于在不同温度下对细菌产物的代谢反应以及行为性发热的有效性等一些重要问题仍然没有答案。许多变温动物，如夜行性无尾两栖类动物，可能在免疫反应期间环境条件限制体温调节的野外环境中活动。在与生态相关但不利的野外热环境条件下，对细菌产物的代谢反应与在发热热偏好温度下测量的反应相比如何？此外，在正常热偏好温度与发热热偏好温度下，与免疫刺激相关的代谢成本分配以及阿伦尼乌斯效应（生化反应速率）是否存在差异？我们比较了未处理和经脂多糖（LPS）处理的黄色库鲁鲁蟾蜍（黄肩蟾蜍）在对应于冬夜野外活动温度、正常热偏好温度和发热热偏好温度下的能量消耗。我们假设在较高体温下对LPS的代谢反应会成比例降低。为了验证这些假设，我们使用琼脂模型在夜间测量野外温度，以及蟾蜍在热梯度中的正常热偏好温度和发热热偏好温度。随后，我们测量了蟾蜍在平均琼脂模型温度、正常热偏好温度和发热热偏好温度下的代谢率。最后，我们计算了在每个这些平均温度下对LPS的代谢反应，即代谢率（MR）与基础代谢率（MR）的比值。我们的结果表明，在这些蟾蜍维持繁殖活动的冬夜典型的琼脂模型温度下，代谢率不会因LPS而增加。此外，在正常热偏好温度下，LPS处理相对于阿伦尼乌斯效应增加了代谢成本，但在发热热偏好温度下没有。这样，在黄色库鲁鲁蟾蜍中，对LPS的代谢反应在发热时比正常热偏好温度下相对更低。
