摘要：

A plasma membrane fraction was obtained from the post-mitochondrial supernatant fraction of bovine adrenal medulla by centrifugation through a continuous sucrose gradient in a zonal rotor.Activities of 5′-nucleotidase (EC 3.1.3.5), (Na+-K+)-ATPase (EC 3.6.1.3), Mg2+-ATPase (EC 3.6.1.3), Ca2+-ATPase (EC 3.6.1.3) and acetylcholinesterase (EC 3.1.1.7) were enriched in this fraction and showed a purification of 8-, 6-, 9-, 11- and 14-fold, respectively, over the whole homogenate.Plasma membranes were reasonably free from mitochondria, microsomes and lysosomes as shown by relatively low activities of cytochrome c oxidase (EC 1.9.3.1), glucose-6-phosphatase (EC 3.1.3.9) and acid phosphatase (EC 3.1.3.2), respectively, and by electron microscopy.The plasma membrane phospholipid fraction contained 4% lysophosphatidyl-choline, 17% sphingomyelin, 38% phosphatidylcholine, 28% phosphatidylethanolamine, 5% phosphatidylserine and 1% each of phosphatidylinositol and phosphatidic acid.

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