NERVE-STIMULATION DECREASES MALONYL-COA IN SKELETAL-MUSCLE

This study was designed to determine the effect of in situ electrical stimulation of the sciatic nerve on malonyl-CoA, an inhibitor of carnitine palmitoyl transferase, in the gastrocnemius/plantaris muscle group of rats. The left sciatic nerve was stimulated at a frequency of 5 Hz with 100-ms trains of impulses (50 Hz) for 1, 3, or 5 min. At the end of stimulation, the left and right (nonstimulated) gastrocnemius/plantaris muscle groups were clamp-frozen and later analyzed for malonyl-CoA and other metabolites. No change was observed in the noncontracting contralateral muscles in malonyl-CoA, ATP, creatine phosphate (CP), or citrate. In the stimulated muscles, malonyl-CoA decreased from 1.7 +/- 0.1 to 1.0 +/- 0.1 nmol/g (P < 0.05), and CP decreased from 15.8 +/- 0.9 to 12.2 +/- 1.0-mu-mol/g (P < 0.05) after 3 min of stimulation. After 5 min of stimulation, malonyl-CoA was 1.0 +/- 0.1 nmol/g and CP was 10.3 +/- 1.3-mu-mol/g. When muscles were stimulated for 5 min with single impulses (5 Hz), malonyl-CoA was decreased from 1.8 +/- 0.3 to 1.0 +/- 0.1 nmol/g, with no change in CP, ATP, or adenosine 3',5'-cyclic monophosphate. Thus a decline in malonyl-CoA can be induced by muscle contraction independently of humoral influence.