The function of cell membrane is considered to have an essential role in transport of metabolites across the cell membrane. The investigation of its function, however, was hampered by the difficulty of obtaining pure preparation of cell membrane. Firstly, Palade l) and Hogeboom et al 2) found “cell membrane” in the nuclear fraction isolated from liver homogenate. In 1960, Neville 3) succeeded in isolating the cell membrane fraction from rat liver, and identified morphologically with electron microscope. His isolation procedure consisted of homogenization with a Dounce homogenizer in 0.001 M NaHCO3 (pH 7.5) followed by sucrose-gradient centrifugation between d = 1.22 and 1.16 at 100,000 g for 75 minutes. Recently, Emmelot and Bos 4) modified the final centrifugation procedure of Neville 3) by separating the membrane fraction between the layers of d = 1.16 and d = 1.22 placed a third layer of sucrose solution of d = 1.20. The modified procedure enabled isolation of the membrane fraction practically free of mitochondria. The preparation was shown to contain no hexokinase, succinate cytochrome c reductase and cytochrome c oxidase activity, but weak activities of glucose-6-phosphatase NADH cytochrome c reductase, and a pronounced ATPase activity were demonstrated. The specific activity of ATPase in the cell membrane fraction was 6 times higher than that of the microsome. In this paper, a modified procedure is presented to attain higher purity of the cell memberane preparation from liver, kidney and testis of rat and rabbit and the results on distribution of ATPase and alkaline phosphtase in four fractions will be reported.
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