Electrical stimulation inactivates muscle acetyl-coa carboxylase
and increases amp-activated protein kinase.
Hutber, C. Adrian, D. G. Hardie, and W. W. Winder.
Zoology Department, Brigham Young University, Provo, Utah 84602 and
Department of Biochemistry, The University, Dundee, DD1 4HN
Scotland
APStracts 3:0224E, 1996.
Muscle malonyl-CoA decreases during exercise or electrical
stimulation, the exercise-induced decline being accompanied by
changes in the kinetic properties (Vmax, K0.5, Ka) of acetyl-CoA
carboxylase (ACC) and by an increase in the AMP-activated protein
kinase activity (AMPK). This study was designed to ascertain whether
the exercise-induced changes are contraction-mediated and, if so, to
follow the time course of these changes. The left sciatic nerve of
rats was stimulated at 1 Hz for 0, 2, 5, 10, 20, or 30 min and the
gastrocnemius/plantaris muscle group was then excised, frozen in
liquid nitrogen, and later analyzed for malonyl-CoA and other
metabolites. ACC and AMPK activities were quantitated in ammonium
sulfate precipitates from homogenates prepared from the frozen
muscles. ACC's Vmax and Ka for citrate decreased and increased
respectively over the first 10 min of stimulation but significantly
increased AMPK activity was not observed until 10 min to 20 min of
stimulation (P < 0.05). Stimulation increased estimated free AMP (P <
0.05). Thus, exercise-induced changes in functional properties of ACC
appear to be contraction-mediated and are accompanied by increased
AMPK activity and by an increase in the estimated free AMP.
Received 2 August 1996; accepted in final form 29 October 1996.
APS Manuscript Number E376-6.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 November 1996