Effect of Post-Mortem Electrical Stimulation on Ovine Sarcoplasmic Reticulum Vesicies

Abstract

Sarcoplasmic reticulum (SR) vesicles from ovine skeletal muscle were iodinated with the use of immobilized lactoperoxidase to determine the location of proteins in the membrane and to observe any changes resulting from post-mortem electrical stimulation. The labelling pattern of the nonstimulated SR preparations was essentially the same as that observed previously for white muscle SR of rabbit. Most of the membrane proteins were labelled, except for the high-affinity calciumbinding protein. Electrical stimulation, however, resulted in an increased labelling of calsequestrin suggesting that this protein is more exposed as a result of such treatment. Certain activities of the adenosinetriphosphatase were affected by electrical stimulation. Both the steady-state concentration of phosphoenzyme and the ATP~PI exchange reaction were significantly reduced by electrical stimulation. It is not known if this alteration in the membrane is responsible for the reduced activity of the SR and thus the greater rate of post-mortem pH fall in electrically stimulated muscle. [Other keywords: Membrane phosphorylation, muscle pH, cold-shortening.]