Plasma membranes of the rat liver. Isolation and enzymatic characterization of a fraction rich in bile canaliculi.
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.
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000469:Alkaline Phosphatase / Q000378:metabolism*; D000818:Animals; D001652:Bile Ducts / Q000166:cytology; D002462:Cell Membrane / Q000201:enzymology*; D002499:Centrifugation, Density Gradient; D003580:Cytochromes; D005952:Glucose-6-Phosphatase / Q000378:metabolism*; D008099:Liver / Q000166:cytology* / Q000201:enzymology; D008854:Microscopy, Electron; D008861:Microsomes / Q000201:enzymology; D009708:Nucleotidases / Q000378:metabolism*; D051381:Rats
D003580:Cytochromes; D009708:Nucleotidases; D000469:Alkaline Phosphatase; D005952:Glucose-6-Phosphatase; D000251:Adenosine Triphosphatases