A thermodynamic-based approach to model the entry into metabolic depression by mammals and birds

AbstractFor 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 (\(\dot{W}\)) was caused by the drop in body temperature, the so-called “Q10 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\(\dot{W}\) from the value maintaining euthermia at a given ambient temperature to the basal metabolic rate of the animal and, then,Q10 effect would take over and drop\(\dot{W}\) 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 equilibriumTb is attained.
Source: Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology - Category: Physiology Source Type: research