Sympathoadrenal system and activation of glycogenolysis during muscular activity

Abstract

Comparisons were made of the appearance of phosphorylase (PHOS) a and lactate (LA) during electrical stimulation of the gastrocnemius (GM) and soleus (SM) muscles of normal and sympathectomized (SYMPX) rats. Ten-second stimulation at 3 Hz increased PHOS a approximately fourfold in the GM of normal rats, whereafter it declined during stimulation until at 60 s it was similar to rest. The increase in PHOS a of GM from SYMPX rats after 10 s of stimulation was approximately 50% that of normal rats. Stimulation of the SM produced smaller and slower increases in PHOS a with the peak occurring after 60 s, which remained constant to 90 s. SYMPX did not alter this effect in the SM. LA production and creatine phosphate depletion in the GM were continuous throughout stimulation and uninfluenced by SYMPX. This was true for the SM with the exception of LA production being greater after SYMPX. [ATP] was unchanged by electrical stimulation. The rate and magnitude of the PHOS a appearance was a function of stimulation frequency. Reversion of PHOS to the b form after stimulation was rapid, with approximately 50% of the peak value being attained in 2.5 s, and at 5 s the values were those of rest. These data demonstrate that an intact sympathoadrenal system is not obligatory for the initiation of glycogenolysis in skeletal muscle.