Functional and metabolic effects of uridine and UTP on the skeletal muscle of the rat submitted to exercise

Twenty millimolar and 2 mM uridine triphosphate and 2 mM uridine were injected intra-arterially into rat leg muscles during a 20 min period of intense exercise and during the recovery phase (20 min). Administration of 20 mM uridine triphosphate during exercise, provoked a complete depression of muscle contractility. On the contrary, supply of 2 mM uridine triphosphate or 20 mM uridine induced a reduction in the decrease of muscular developed tension during the exercise period of time and favoured functional recovery. This positive effect of pyrimidine compounds on muscular functional parameters did not seem to be correlated with metabolic effects. Indeed, 2 mM uridine supply did not modify the evolution of intramuscular glycogen and lactate concentrations and made worsened the adenine nucleotide degradation induced by exercise.