Suppression of Metabolism during Hibernation in Ground Squirrels (Citellus lateralis)

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Abstract
The euthermia-to-hibernation Q10 of metabolic rate (MR) for some hibernators is reported to be greater than 3.0, which suggests that decrease in tissue temperature alone cannot explain the decrease in MR observed in hibernation. It has been proposed that respiratory acidosis is a possible mechanism for suppressing MR below basal levels during entrance into torpor. Data from 11 ground squirrels (Citellus lateralis) indicate that respiratory acidosis occurs during hibernation but that its role may be limited to suppression of thermoregulatory thermogenesis and not suppression of metabolism below basal levels. Retention of CO₂ and onset of acidosis are reflected in transient decreases in respiratory quotient (RQ) during early entrance (.81–.74–.87). Reversal of the acidosis is indicated by transient increases in RQ immediately prior to arousal (.78–1.10–.78). However, Q10 calculations reveal that differences between sleeping MR at thermoneutrality and deep hibernation MR can be explained by the influence of temperature on tissue metabolism (mean Q10 = 2.5). In this study, Q10's greater than 3.0 resulted only from comparisons of deep hibernation MR, with resting MR under nonthermoneutral conditions prior to or during initial entrance (body temperature > 34 C).

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