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Adaptive thermogenesis in hummingbirds

José Eduardo P. W. Bicudo^1,*, Antonio C. Bianco² and Cláudia R. Vianna^1,3

¹ Department of Physiology, Biosciences Institute, University of São Paulo, SP, Brazil
² Thyroid Division, Department of Medicine, Brigham & Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
³ Division of Endocrinology, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02115, USA
^* Present address: Departmento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, 05508-900 São Paulo, SP, Brazil

View larger version (17K): [in a new window]   Fig. 1. Evolutionary tree of uncoupling proteins (UCPs) and other mitochondrial carriers. The unrooted evolutionary tree represents inferred genetic distances (the numerical values indicate the number of base substitutions that change the amino acid sequences) between UCP sequences obtained from GeneBank (Protpars program from PHYLIP package) (Felsenstein, 1988). Abbreviations, species and accession numbers are as follows: HuUCP1 is Homo sapiens (human) UCP1, P25874; OcUCP1 is Oryctolagus cuniculus (rabbit) UCP1, P14271; RnUCP1 is Rattus norvegicus (rat) UCP1, P04633; HmUCP is Eupetomena macroura (hummingbird) UCP, AF255729; SsUCP2 is Sus scrofa (pig) UCP2, AAD05201; MmUCP2 is Mus musculus (mouse) UCP2, P70406; CcUCP2 is Cyprinus carpio (carp) UCP2, CAB46248; DrUCP2 is Danio rerio (zebrafish) UCP2, CAB46268; BtUCP3 is Bos taurus (cow) UCP3, AAC61762; HuUCP3 is H. sapiens (human) UCP3, P55916; StUCP is Solanum tuberosum (potato) UCP, CAA72107; AtUCP is Arabidopsis thaliana (thale cress) UCP, CAA77109; BtMPCP is B. taurus (cow) mitochondrial carrier protein, P12234; MmBMCP1 is M. musculus (mouse) brain mitochondrial carrier protein, AAD03674; CeSMCF is Caenorhabditis elegans (worm) similar mitochondrial carrier family, AAB54239; HuUCP4 is H. sapiens (human) UCP4, AAD16995; HuADP/ATP1 is H. sapiens (human) ADP/ATP translocator, P12235; RnADP/ATP1 is R. norgevicus (rat) ADP/ATP carrier, Q05962. Reproduced from Vianna et al. (2001) with permission from the American Physiological Society.

View larger version (20K): [in a new window]   Fig. 2. Hummingbird uncoupling protein (HmUCP) expression in yeast and HmUCP-induced mitochondrial uncoupling. (A) Western blot detection of 12CA5-tagged HmUCP in isolated yeast mitochondria after 12 h of induction with 1 % galactose using anti-12CA5 antibodies. Cells transformed with empty pYES2 vector were used as negative controls. (B) Flow cytometry analysis of mitochondrial membrane potential following the expression of HmUCP in yeast. Rat UCP1 and empty pYES2 vector were used as positive and negative controls, respectively. Yeast cells were incubated in DiOC6-sensitive dye. The x-axis is a logarithmic scale of fluorescence intensity, and the y-axis represents the number of cells. A shift of the curve towards the left indicates a decreased mitochondrial membrane potential. Reproduced from Vianna et al. (2001) with permission from the American Physiological Society.

View larger version (28K): [in a new window]   Fig. 3. Changes in hummingbird uncoupling protein (HmUCP) mRNA levels during torpor and rewarming. (A) Profile of the rate of oxygen consumption of a representative specimen of Eupetomena macroura during euthermy, torpor and rewarming. Body temperatures were 33-40 °C and 15-23 °C during euthermy and torpor, respectively. (B) Northern blot of total RNA (probed with [-32P]dCTP-labelled HmUCP coding region) obtained from heart and pectoral (wing) muscle of birds killed at the indicated times of the torpor/rewarming cycle. E, euthermy; T, torpor; R, rewarming. The ribosomal (18S) RNA was stained with Methylene Blue. (C) Ratio between HmUCP mRNA and ribosomal RNA obtained after densitometry. Values are the mean + range. Two animals were used per activity state. *P<0.05 compared with euthermy (E); **P0.05 compared with rewarming (R) (ANOVA). Reproduced from Vianna et al. (2001) with permission from the American Physiological Society.