caa a22 4500 465826202 CHVBK 20180323112150.0 cr unu---uuuuu 170327e19901101xx s 000 0 eng 10.1007/BF00691712 doi (NATIONALLICENCE)springer-10.1007/BF00691712 Relationships between body temperature, thermal conductance, Q 10 and energy metabolism during daily torpor and hibernation in rodents [Elektronische Daten] [Gregory Snyder, James Nestler] Summary: In the present paper we examine the ability of rodents to maintain body temperature (T B ) following the marked reductions in metabolic heat production associated with torpor. Previously published values for metabolic rate (M),T B and ambient temperature (T A ) were used to calculate thermal conductances (C') during normothermy and torpor in rodents capable of daily torpor (11 species) and hibernation (18 species). Values ofC' for torpid animals are uniformly lower thanC' in normothermic animals. In addition,C' of normothermic and torpid rodents decreases with increasing body mass (BM). However, the slope of the relationship betweenC' and BM is almost 4-fold greater for normothermic than for torpid animals. Thus, the ability of torpid rodents to conserve body heat by reducingC' decreases with increasing mass. Rodents that use daily torpor tend to be small and they tend to maintainT B well aboveT A during torpor. Hibernators tend to be larger and regulateT B relatively close toT A . Thus, the reductions inC' appear to be closely correlated with the level ofT B regulation during torpor. We suggest that the changes inC' represent a suite of physiological adaptations that have played a central role in the evolution of torpor, enabling rodents to regulateT B aboveT B during periods of very low heat production. Based on the approach used here we address the controversy of whether reductions inM during torpor are due entirely to temperature effects or whether metabolic inhibition in addition to temperature effects may be important. We suggest that the controversy has been confused by usingQ 10 to evaluate the relationship ofM andT B in endotherms. What is perceived as metabolic inhibition (i.e.,Q 10>3) is confounded by changes in the relationship ofM andT B due to reductions inC' and reductions in the difference betweenT B andT A . Unfortunately, changes inM andT B cannot be used to quantify changes in metabolic state in endotherms. Thus, neitherQ 10 nor the approach used here can be used to make valid statements about the metabolic regulatory processes associated with torpor. Other methods, perhaps at the cell or tissue level, are needed. Springer-Verlag, 1990 Adaptive hypothermia nationallicence Controlled hypothermia nationallicence T B : body temperature nationallicence T A : ambient temperature nationallicence C' : thermal conductance nationallicence C n′ : normothermicC ′ whenT A is above a lower critical temperature nationallicence C t′ : torporC ′ when animals are in daily torpor or hibernation nationallicence M : metabolic rate nationallicence BM : body mass nationallicence WVPD : water vapor pressure deficit nationallicence Snyder Gregory Department of Environmental, Population and Organismic Biology, University of Colorado, 80309, Boulder, Colorado, USA aut Nestler James Department of Environmental, Population and Organismic Biology, University of Colorado, 80309, Boulder, Colorado, USA aut Journal of Comparative Physiology B Springer-Verlag 159/6(1990-11-01), 667-675 0174-1578 159:6<667 1990 159 360 https://doi.org/10.1007/BF00691712 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00691712 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Snyder Gregory Department of Environmental, Population and Organismic Biology, University of Colorado, 80309, Boulder, Colorado, USA aut NATIONALLICENCE 700 1- Nestler James Department of Environmental, Population and Organismic Biology, University of Colorado, 80309, Boulder, Colorado, USA aut NATIONALLICENCE 773 0- Journal of Comparative Physiology B Springer-Verlag 159/6(1990-11-01), 667-675 0174-1578 159:6<667 1990 159 360 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer