Laboratório de Energética e Fisiologia Teórica, Departamento de Fisiologia, Instituto de Biociências da Universidade de São Paulo, Rua do Matão, 101, Butantã, São Paulo, SP, CEP: 05508-090, Brazil.
J Comp Physiol B. 2022 Sep;192(5):593-610. doi: 10.1007/s00360-022-01442-9. Epub 2022 Jun 23.
For decades, there was an intense debate in relation to the mechanism behind the entry into metabolic depression (EMD) of mammals and birds. The fulcrum of the argument was whether the depression of metabolic rate ([Formula: see text]) was caused by the drop in body temperature, the so-called "Q effect", or whether it was caused by a metabolic downregulation. One present-day model of this process is a qualitative (textual) description: the initial step of EDM would be a downregulation in [Formula: see text] from the value maintaining euthermia at a given ambient temperature to the basal metabolic rate of the animal and, then, Q effect would take over and drop [Formula: see text] to its lower levels. Despite widely accepted, this qualitative description still misses a theoretical analysis. Here, we transpose the descriptive model to a formal quantitative one and analyze it under necessary thermodynamic conditions of a system. We, then, compare the results of the formal model to empirical data of EMD by mammals and birds. The comparisons indicate that the metabolic evolution in the course of the entry phase does not follow the descriptive model. Instead, as proposed by alternate models, EMD is a downregulated process as a whole until a new equilibrium T is attained.
几十年来，关于哺乳动物和鸟类进入代谢抑制（EMD）的机制一直存在激烈的争论。争论的焦点是代谢率下降（[Formula: see text]）是由体温下降引起的，即所谓的“Q 效应”，还是由代谢下调引起的。目前对此过程的一个模型是定性（文字）描述：EDM 的初始步骤是下调[Formula: see text]，使其从维持特定环境温度下的体热值降至动物的基础代谢率，然后 Q 效应接管并将[Formula: see text]降至较低水平。尽管这一描述被广泛接受，但它仍然缺乏理论分析。在这里，我们将描述性模型转换为形式化的定量模型，并在系统的必要热力学条件下对其进行分析。然后，我们将形式模型的结果与哺乳动物和鸟类的 EMD 实证数据进行比较。比较表明，在进入阶段的代谢进化并不遵循描述性模型。相反，正如替代模型所提出的，EMD 是一个整体下调的过程，直到达到新的平衡 T。
