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metabolism and thermoregulation



A while back, George O. wrote to the list asking how heat is generated
in endothermic animals.  I was surprised that nobody responded but
also didn't feel competent to respond myself.  Now, however, I can at
least point George (and anyone else interested) in the right direction
for further research.

In endothermic animals, there are proteins which "uncouple" some of
the metabolic activity of mitochondria from one of their major roles
as producers of ATP.  That is, instead of building higher energy
molecules which other organelles will use to drive their normal
operations, the mitochondria burn oxygen and fatty acids for
essentially nothing more than the production of heat.  (I still can't
say I know much about this, so feel free to correct me anyone -- in
fact, one of the papers I'm going to recommend below appears to
suggest an alternative mechanism).

If you want to start digging into the literature, I can recommend a
few recent articles based on an *extremely* cursory search:

 Author(s):      SAZANOV LA; JACKSON JB 
 Title:          PROTON-TRANSLOCATING TRANSHYDROGENASE AND NAD-LINKED AND NADP-
                   LINKED ISOCITRATE DEHYDROGENASES OPERATE IN A SUBSTRATE 
                   CYCLE WHICH CONTRIBUTES TO FINE REGULATION OF THE 
                   TRICARBOXYLIC-ACID CYCLE ACTIVITY IN MITOCHONDRIA 
                    
 Source:         FEBS LETTERS V0344 N2-3 MAY 16 1994 pp. 109-116. 
---                    
 Author(s):      DESAUTELS M; DULOS RA 
 Title:          TEMPERATURE AND PHENYLMETHYLSULFONYL FLUORIDE SENSITIVE LOSS 
                   OF UNCOUPLING PROTEIN IN ISOLATED BROWN ADIPOSE-TISSUE 
                   MITOCHONDRIAL-MEMBRANES 
                    
 Source:         BIOCHEMISTRY AND CELL BIOLOGY-BIOCHIMIE ET BIOLOGIE CELLULAIRE 
                   V0072 N1-2 JAN-FEB 1994 pp. 1-7. 
---                    
 Author(s):      YAMASHITA H; YAMAMOTO M; OOKAWARA T; SATO Y; UENO N; OHNO H
 Title:          DISCORDANCE BETWEEN THERMOGENIC ACTIVITY AND EXPRESSION OF 
                   UNCOUPLING PROTEIN IN BROWN ADIPOSE-TISSUE OF OLD RATS 
                    
 Source:         JOURNALS OF GERONTOLOGY V0049 N2 MAR 1994 pp. B  54-B  59.
---                    
 Author(s):      TATELMAN HM; TALAN MI 
 Title:          METABOLIC HEAT-PRODUCTION AND COLD TOLERANCE DURING COLD 
                   STRESS OF DIFFERENT INTENSITY OF ADULT AND AGED MALE 
                   C57BL/6J MICE
 
 Source:         EXPERIMENTAL GERONTOLOGY V0028 N6 NOV-DEC 1993 pp. 579-584. 
--- 
 Author(s):      DUCHAMP C; CHATONNET J; DITTMAR A; BARRE H
 Title:          INCREASED ROLE OF SKELETAL-MUSCLE IN THE CALORIGENIC RESPONSE 
                   TO GLUCAGON OF COLD-ACCLIMATED DUCKLINGS 
                    
 Source:         AMERICAN JOURNAL OF PHYSIOLOGY V0265 N5 P2 NOV 1993 pp. R1084-
                   R1091. 
---                    
 Author(s):      KORTNER G; SCHILDHAUER K; PETROVA O; SCHMIDT I
 Title:          RAPID CHANGES IN METABOLIC COLD DEFENSE AND GDP BINDING TO 
                   BROWN ADIPOSE-TISSUE MITOCHONDRIA OF RAT PUPS
                    
 Source:         AMERICAN JOURNAL OF PHYSIOLOGY V0264 N5 P2 MAY 1993 pp. R1017-
                   R1023. 

-- 
Mickey Rowe     (rowe@lepomis.psych.upenn.edu)