Does Active Metabolic Suppression Occur During Entry into Torpor

KARPOVICH, S.*; TOIEN, O.; BARNES, B.M.: Does Active Metabolic Suppression Occur During Entry into Torpor?

Captive S. parryii from Toolik Lake, Alaska were housed at University of Alaska Fairbanks and exposed to ambient temperatures (Ta) of +2, -5 and -12oC. Body temperature (Tb) was recorded via telemetry and rates of oxygen consumption (VO2) and carbon dioxide production were measured with open flow respirometry to estimate the energetic costs of ground squirrels during the re-entry phase of arousal episodes. Explanations of the mechanisms that allow hibernators to depress metabolic rate during entry into torpor are controversial. Does metabolic rate drop as a consequence of Q10 effects accompanying decreased Tb or Tbrain, OR does Tb decrease as a result of temperature-independent metabolic suppression? Preliminary data indicates that Q10 of Tb vs. VO2 for trials at each Ta (+2, -5 and -12oC)average 5, which is above the biologically expected Q10 range of 2-3. This indicates metabolic suppression independent of body temperature. Rates of Tb cooling curves are different for trials run at the 3 Tas, with no change in the rate of VO2 decrease. This also supports the metabolic suppression theory. Tbrain data will be examined.

the Society for
Integrative &