Skeletal muscle glycogen depletion during submaximal exercise in rats with chronic heart failure

The purpose of the present study was to determine whether or not abnormalities in glycogen utilization occur in the working skeletal muscles of rats with a myocardial infarction (MI) and chronic heart failure (CHF). Accordingly, glycogen concentrations were measured at rest and following 45 min of submaximal swimming in noninfarcted (SHAM) and MI rats. The tissues examined included the liver and the vastus intermedius, plantaris, soleus and the white portions of the gastrocnemius and tibialis anterior muscles of the rat's hindlimb. Results were analyzed by a two-way analysis of variance and demonstrated that the exercise protocol produced a significant amount of glycogen depletion in the liver and the vastus intermedius and plantaris muscles of the SHAM and MI groups of rats. Although the amount of glycogen utilized in the liver was similar between the SHAM and MI groups of rats, the amount of glycogen utilized in the vastus intermedius and plantaris muscle was significantly greater for the MI group of rats when compared to their SHAM counterparts. The results suggest that the glycogen depletion abnormalities found in the working muscles of the MI rat with CHF are related to accelerated rates of glycogen breakdown and utilization. Furthermore, the results also support the contention that these glycogen depletion abnormalities are primarily located in muscles that are primarily oxidative in nature. The mechanisms responsible for these abnormalities in skeletal muscle glycogen utilization during exercise in the MI rat with CHF have yet to be determined.