Ww. Winder et al., EFFECT OF ADRENODEMEDULLATION ON DECLINE IN MUSCLE MALONYL-COA DURINGEXERCISE, Journal of applied physiology, 74(5), 1993, pp. 2548-2551
Malonyl-CoA is an inhibitor of carnitine palmitoyltransferase, a rate-
limiting enzyme of fatty acid oxidation. Previous studies have indicat
ed that muscle malonyl-CoA declines in rats during treadmill running.
This decrease may be important for allowing an increased rate of fatty
acid oxidation during prolonged exercise. This study was designed to
determine whether epinephrine is essential for inducing the decline in
muscle malonyl-CoA during exercise. Male Sprague-Dawley rats underwen
t adrenodemedullation (ADM) or sham operation. After allowing 3 wk for
recovery, rats were killed (pentobarbital anesthesia) at rest or afte
r running at 21 m/min up a 15% grade for 60 min. Red quadriceps malony
l-CoA decreased from 2.6 +/- 0.3 to 0.8 +/- 0.07 nmol/g in sham-operat
ed rats and from 2.2 +/- 0.3 to 0.8 +/- 0.1 nmol/g in ADM rats. White
quadriceps malonyl-CoA decreased to similar levels during exercise in
both sham-operated and ADM rats. A second experiment on 24-h fasted ra
ts also showed no impairment in the exercise-induced decline in red qu
adriceps malonyl-CoA as a result of adrenodemedullation. The hormones
of the adrenal medulla are therefore unessential for inducing the decl
ine in malonyl-CoA during exercise.