POSTEXERCISE RECOVERY OF SKELETAL-MUSCLE MALONYL-COA, ACETYL-COA CARBOXYLASE, AND AMP-ACTIVATED PROTEIN-KINASE

Previous studies have demonstrated that oxygen consumption and fat oxi dation remain elevated in the postexercise period. The purpose of this study was to determine whether malonyl-CoA, an inhibitor of fatty aci d oxidation, remains depressed in muscle after exercise. Rats were spr inted for 5 min (40 m/min, 5% grade) or run for 30 min (21 m/min, 15% grade). Red quadriceps malonyl-CoA returned to resting values by 90 mi n postexercise in the sprinting rats and remained significantly lower at least 90 min postexercise in the 30-min exercise group. AMP-activat ed protein kinase activity remained significantly elevated (P < 0.05) for 10 min after exercise in both groups. The most rapid rate of glyco gen repletion was in the first 30 min postexercise. The respiratory ex change ratio decreased from a nonexercise value of 0.87 +/- 0.01 to an average 0.82 +/- 0.01 during the 90-min period after 30 min of exerci se. Thus muscle malonyl-CoA remains depressed and fat oxidation is ele vated for relatively prolonged periods after a single bout of exercise . This may allow fat oxidation to contribute more to muscle energy req uirements, thus leaving more glucose for replenishment of muscle glyco gen.