Work induced myocardial glycogen resynthesis.

Work induced myocardial glycogen repletion was studied in an isolated perfused heart preparation. After 15 min of low or high workload perfusion with substrate free buffer, glycogen was depleted by 29% (p < .05) and 61% (p < .001) respectively. During the resynthesis phase with 11 mM glucose as substrate, glycogen was increased by 23% (p < .05) and 44% (p < .01) for the moderately and severely depleted hearts. The rate of glycogen resynthesis was 2.4 fold greater in the more severely depleted hearts. Providing the substrate depleted myocardium with 5.5 mM, 11 mM or 22 mM glucose during the recovery period resulted in glycogen resynthesis of 9.01, 9.95 and 16.53 mg/hr/gm dry wt. When severely depleted hearts were provided with 11 mM glucose or a combination of 11 mM glucose and 5 mM sodium pyruvate, glycogen repletion was 9.95 and 16.50 mg/hr/gm dry wt. These experiments indicate that an isolated perfused heart can be used to study work induced glycogen repletion which is responsive to a change in the preceding workload, substrate concentration and the availability of an alternative carbon source.