Effect of denervation on fragmented sarcoplasmic reticulum of white and red muscle

Abstract

Denervation produces a transient increase (maximum at 15 days) in calcium uptake measured in the presence of oxalate of the fragmented sarcoplasmic reticulum; in 6 weeks the values are back to or below normal. ATPase activity increased steadily during the same period; this increase is attributable to the so-called basal, Ca 2+-independent component. In contrast, calcium uptake without oxalate and initial rates of uptake with or without oxalate show only a decrease, and incorporation of 32P from γ-labeled ATP into an acid-stable protein complex decreases in a parallel fashion. The rate of release of Ca 2+ from preloaded vesicles in the presence of EGTA or caffeine increases after denervation. The effect of denervation affects both white and red muscles, although the changes in the latter are smaller and confined to the ATPase activity. The observations are discussed in terms of changes in altered membrane structure, manifested in increased leakiness and changes in the size of the vesicles found in fragmented sarcoplasmic reticulum.