Effect of post-mortem electrical stimulation on ovine sarcoplasmic reticulum vesicles

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 non-stimulated SR preparations was esentially the same as that observed previously for white muscle SR of rabbit. Most of the membrane protein were labelled, except for the high-affinity calcium-binding 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 in equilibrium 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 in electrically stimulated muscle.