SIDEDNESS AND PERMEABILITY OF SARCOLEMMAL MEMBRANES ISOLATED FROM NORMAL AND DENERVATED RAT SKELETAL-MUSCLE

Sarcolemmal membranes of normal and denervated rat skeletal muscle were prepared by a LiBr/KCl extraction procedure and characterized with respect to their membrane sidedness and permeability. These parameters were determined by measuring latent ouabain sensitive (Na+,K+)-ATPase and acetylcholinesterase activities following perturbation of sarcolemmal membranes with Sodium Dodecyl Sulphate (SDS). Results indicate that the majority of the normal membrane vesicles are leaky in nature with less than one-third of the total membrane population isolated as sealed vesicles, orientated inside-out. No significant change to either membrane sidedness or permeability could be detected in denervated membranes. Our results together with a previous study (18) suggest that the orientation and integrity of membranes isolated from normal and denervated muscle are not differentially altered by the LiBr/KCl extraction procedure. The significance of these results is discussed with respect to alterations in Concanavalin A (ConA) binding to rat skeletal muscle sarcolemmal membranes following denervation.