CHATONNET, J. 
THE ROLE OF EPINEPHRINE SECRETION 
Can the calorigenic action of hormones of the adrenal medulla 
play an important part in the regulatory heat production? In 1941, 
Hemingway and Hathaway ascribed to this factor the slight increase 
of metabolism observed at the beginning of the cold exposure, be- 
fore the onset of shivering. Of course, extraneous injected epineph- 
rine can substitute for the heat required by the cold exposure. How- 
ever, Lundholm (1949) estimated a maximum augmentation of basal 
combustions by epinephrine injection of only 28 per cent. But, 
sensitization of that action can be provided by acclimation (Cottle 
and Carlson, 1956). In experiments on removal of the adrenal med- 
ulla in the rat, Thibault (1948) estimates that epinephrine contributes 
as much as 35 to 40 per cent to the total power of thermogenesis. 
In the dog, such a procedure is inefficient, even in very cold envir- 
onments, because of the importance of other substitutes. 
In order to avoid these difficulties, we have tried first to elim- 
inate an important part of the muscular innervation, leaving the 
spinal control of epinephrine secretion intact, by section of the 
brachial plexus, associated with section of the roots of the spinal 
cord below lumbar two level. A maximum metabolism is still 
reached. Then, one adrenal medulla is denervated and cleaned, and 
the other gland removed. A significant but rather mild lowering of 
the maximum metabolism level is obtained (50 to 100 per cent of 
the basal metabolism) (Fig. 4). Probably the main role of the sym- 
pathicoadrenal system in the defense against cold consists of the 
reduction of heat loss. 
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