Effect of uridine supply on glycogen resynthesis after ischaemia in the isolated perfused rat heart

Isolated rat hearts were subjected to 30 min low flow ischaemia (0.5 ml X min-1). During reperfusion, uridine (5 X 10(-5) mol X litre-1) was added to the perfusion medium for 30 min. The concentrations of creatine phosphate, adenine nucleotides, uridylic nucleotides and glycogen were determined at the end of the experiments. The purpose of this work was to study the effects of uridine supply on the concentration of energetic compounds during reperfusion recovery. Low flow ischaemia induced a breakdown of creatine phosphate, adenosine triphosphate, and total adenine nucleotides by 53%, 23% and 15% respectively. The creatine phosphate content was restored during reperfusion without uridine, but the adenine nucleotides remained unchanged. The uridylic nucleotides and the glycogen were also degraded during ischaemia by 56% and 53% for uridine triphosphate and glycogen respectively. Reperfusion without uridine induced a partial resynthetisation of uridylic nucleotides but glycogen stores were not significantly restored. When tested in oxygenated hearts, uridine supply induced a fall in creatine phosphate concentration and an enhancement of uridine triphosphate level but it had no effect on adenosine triphosphate, uridine diphosphate glucose or glycogen concentrations. If supplied during reperfusion, the nucleoside induced the complete restoration of myocardial ATP, total adenine nucleotide content, an increase in the uridylic nucleotide concentration and the resynthetisation of glycogen to supra-normal value.