I. De Glisezinski et al., Lack of alpha(2)-adrenergic antilipolytic effect during exercise in subcutaneous adipose tissue of trained men, J APP PHYSL, 91(4), 2001, pp. 1760-1765
The aim of this study was to investigate the involvement of the antilipolyt
ic alpha (2)-adrenergic receptor pathway in the regulation of lipolysis dur
ing exercise in subcutaneous abdominal adipose tissue (SCAAT). Seven traine
d men and 15 untrained men were studied. With the use of microdialysis, the
extracellular glycerol concentration was measured in SCAAT at rest and dur
ing 60 min of exercise at 50% of maximal oxygen consumption. One microdialy
sis probe was perfused with Ringer solution; the other was supplemented wit
h phentolamine (alpha (2)-adrenergic receptor antagonist). No differences i
n baseline extracellular or plasma glycerol concentrations were found betwe
en the two groups. The exercise-induced extracellular and plasma glycerol i
ncrease was higher in trained compared with untrained subjects (P < 0.05).
Addition of phentolamine to the perfusate enhanced the exercise-induced res
ponse of extracellular glycerol in untrained subjects but not in trained su
bjects. The exercise-induced increase in plasma norepinephrine and epinephr
ine concentrations and the decrease in plasma insulin were not different in
the two groups. These in vivo findings demonstrate higher exercise-induced
lipolysis in trained compared with untrained subjects and show that, in tr
ained subjects, the <alpha>(2)-mediated antilipolytic action is not involve
d in the regulation of lipolysis in SCAAT during exercise.