Plasma membranes of the rat liver. Isolation and enzymatic characterization of a fraction rich in bile canaliculi |
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Authors: | C S Song W Rubin A B Rifkind A Kappas |
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Institution: | From The Rockefeller University and the Departments of Medicine and Anatomy, Cornell University Medical College, New York 10021 |
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Abstract: | A method is described for the rapid isolation of a plasma membrane fraction containing a high concentration of intact bile canaliculi from the rat liver. Isolated bile canaliculi retain most of the ultrastructural features exhibited in the intact liver cell. The final fraction contains 5''-nucleotidase activity at approximately the same concentration as that in previous preparations of plasma membranes. In the presence of 0.01 M Mg++, 5''-nucleotidase exhibits a double pH optimum at pH values of 7.5 and 9.5. The activities of glucose-6-phosphatase and alkaline phosphatase are present in low amounts. Cytochrome P-450 is not detectable. Na+-K+-activation of ATPase is observed to the extent of 20–36% in about half of the assays. The availability of a method for preparation of intact bile canaliculi should prove useful for studying the biochemical events associated with the transport of bile constituents into canaliculi. |
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