Preparation and properties of highly enriched cardiac sarcolemma from isolated adult myocytes.

Isolated myocytes were prepared from adult canine hearts using a combined technique of myocardial perfusion followed by incubation with collagenase. More than 60% of the cells routinely excluded trypan blue dye. Disruption of the myocytes was accomplished using high pressure nitrogen cavitation. After differential and sucrose gradient centrifugation, the peak sarcolemmal fraction averaged 100-fold enrichment in ouabain-inhibited K+-stimulated p-nitrophenyl phosphatase and 82-fold in ouabain-inhibited (Na+,K+)-ATPase. These sarcolemmal membranes are enriched in phospholipid phosphorus (1.98 mumol/mg of protein) and more than 4-fold in sphingomyelin and cholesterol. Polyacrylamide gels revealed three major protein peaks at 50,000, 91,000, and 140,000 apparent molecular weights. This work demonstrates the feasibility of preparing highly pure cardiac sarcolemma from isolated adult myocytes. The problem of cellular cross-contamination due to heterogeneity of cell types in whole myocardial tissue has been circumvented. The level of enrichment exceeds all reported preparations of cardiac sarcolemma from whole myocardium and cultured myocytes. This preparation should prove to be useful as an in vitro model for studies of physiological, pharmacological, and pathological perturbations of sarcolemmal structure and function.