Effect of high-protein diet on glycolytic processes in skeletal muscles of exercising rats

The aim of the study was to assess the effort capacity of rats subjected to combined effects of high-protein diet (protein 49%; carbohydrate 30%) and endurance training. The measure of the animal fitness was the time of running to exhaustion on a treadmill. The changes in carbohydrate content including hepatic and muscular glycogen, peripheral blood glucose concentration and activity of some glycolytic enzymes in red slow oxidative (SO) and white fast glycolytic (FG) fibres of the gastrocnemius muscle were analysed. Samples of skeletal muscles, liver and blood were taken after one month on the high-protein diet and/or physical exercise. A high protein level in the diet caused no change in the effort capacity of rats but decreased the capability of carbohydrate accumulation in the skeletal muscles. The observed disturbances of the post-exercise activity of hexokinase and pyruvate kinase (in both) types of fibres) and phosphoglycomutase (specially in FG fibres) suggest that the protein enriched died limits the extent of glycolysis processes. Despite of this the effort capacity of animals is kept on the same level as in the case of a standard diet. These results suggest that some other metabolic adaptations were developed which allow to continue the exercise.