Abstract
INTRODUCTION: Because impaired excitation-contraction coupling and reduced sarcoplasmic reticulum (SR) Ca(2+) release may contribute to the age-associated decline in skeletal muscle strength, we investigated the effect of aging on regulation of the skeletal muscle isoform of the ryanodine receptor (RyR1) by physiological channel ligands. METHODS: [(3) H]Ryanodine binding to membranes from 8- and 26-month-old Fischer 344 extensor digitorum longus (EDL) and soleus muscles was used to investigate the effects of age on RyR1 modulation by Ca(2+) and calmodulin (CaM). RESULTS: Aging reduced maximal Ca(2+) -stimulated binding to EDL membranes. In 0.3 μM Ca(2+) , age reduced binding and CaM increased binding to EDL membranes. In 300 μM Ca(2+) , CaM reduced binding, but the age effect was not significant. Aging did not affect Ca(2+) or CaM regulation of soleus RyR1. DISCUSSION: In aged fast-twitch muscle, impaired RyR1 Ca(2+) regulation may contribute to lower SR Ca(2+) release and reduced muscle function. Muscle Nerve 57: 1022-1025, 2018.