STUDIES ON THE GLYCOGEN METABOLISM OF ATROPHIC AND REGENERATING MUSCLE

Abstract

Expts. were carried out on the gastroc-nemius muscles of adult albino rats. Denervation, immobilization by casts and tenotomy were followed in a few days by comparable marked falls in the glycogen conc. of the affected muscles. The glycogen changes occurred at a greater velocity than the loss of creatine, mass or strength from atrophic muscles. Conversely, restoration of muscle function through nerve regeneration, regrowth of tendon and cast removal was followed by a rapid and complete restoration of glycogen conc. to normal levels sooner than the recovery of creatine, mass or strength. Adrenalectomy did not prevent the fall in glycogen concentration in denervated muscle. Even though the fall in glycogen conc. and subsequent recovery coincides in time with the appearance and disappearance of fibrillary activity, it is believed that fibrillary contractions per se are not the cause of the low glycogen conc. in denervated muscle. The finding of equally marked and rapid decreases in the glycogen conc. of muscle undergoing atrophy without fibrillary activity, the fact that quinidine abolishes fibrillary activity without preventing the fall in glycogen and the observation that electrical stimulation will lessen rather than enhance the loss of glycogen from denervated muscle, indicate fundamental causes other than fibrillary activity. It is suggested that the absence of tension development in the atrophic muscle results in insufficient energy levels for the coupled reactions which may be required for glycogen synthesis.