Journal of Applied Physiology, Vol 42, Issue 6 884-888, Copyright © 1977 by American Physiological Society
Effect of physical training on control mechanisms of lipolysis in rat fat cell ghosts
R. E. Shepherd, W. L. Sembrowich, H. E. Green and P. D. Gollnick
Fat cell ghosts and homogenates of fat cells were used to study the
influence of training on the regulatory system for lipolysis in adipose
tissue of female rats. A training effect was identified from elevated
succinate dehydrogenase activities in the soleus and plantaris muscles.
Neither basal nor maximal (NaF-stimulated) adenylate cyclase activities per
mg protein of fat cell ghosts were altered by training. Fluoride-stimulated
adenylate cyclase activity per microgram DNA was lower in the trained than
untrained group. Adenylate cyclase activities in response to norepinephrine
expressed either on a per mg protein or per microgram DNA basis were lower
(P less than 0.05) in fat cell ghosts from trained rats. Phosphodiesterase
activity was higher (P less than 0.05) in fat cell ghosts from trained rats
for cyclic AMP concentrations of 1--5.0 micrometer. The apparent Km's of
phosphodiesterase were 1.19 and 2.0 micrometer of cyclic AMP for the
untrained and trained groups, respectively (P less than 0.05). Protein
kinase activity in the supernatant fraction of homogenates of fat cells was
unchanged due to training. The overall effect of training was to blunt the
system for cyclic AMP production in rat adipocytes. This may explain, at
least partially, the lower plasma free fatty acid levels observed in
trained compared to untrained persons during submaximal exercise.
