RYANODINE AND THEOPHYLLINE-INDUCED DEPLETION OF ENERGY STORES IN AMPHIBIAN MUSCLE

The effects of high and low levels of ryanodine on theophylline-induce d energy depletion were studied in isolated frog sartorius muscle. Whe reas low concentrations of ryanodine (1-10 mu M) did not change high e nergy phosphate contents (PE) after 60 min, high levels (100 mu M) red uced resting energy contents by 60% after 60 min. Subcontracture level s of theophylline (2 mM), in the presence of high ryanodine, produced an 80% PE depletion, suggesting possible additive or synergistic effec ts of these two agents. In contrast to theophylline-induced depletion, neither the ryanodine-induced depletion nor the theephylline-plus-rya nodine-induced depletion of PE seemed sensitive to inhibition by 1 mM procaine. This suggests that there may be differences in the mechanism s whereby methylxanthines and ryanodine deplete energy stores and evok e contractures in amphibian skeletal muscle.