Cytochromes P-450 in human hepatocyte plasma membrane: recognition by several autoantibodies.
BACKGROUND
Anti-cytochrome P-450 autoantibodies are present in several forms of autoimmune hepatitis. The possibility that cytochromes P-450 are present in the plasma membrane of human hepatocytes was examined.


METHODS
(1) Plasma membranes with microsomal contamination < 1%, as judged from the activities of glucose-6-phosphatase and NADH-cytochrome c reductase, were prepared. (2) After exposure of uncut, fixed hepatocytes to antibodies, immunofluorescence and immunoperoxidase studies were performed.


RESULTS
(1) The specific content of cytochrome P-450 in plasma membrane was 9% of that in microsomes. Plasma membranes showed NADPH-cytochrome c reductase and mono-oxygenase activities; immunoblots showed the presence of cytochromes P-450 1A2, 2C, 2D6, 2E1, and 3A4; cytochromes P-450 1A2, 2D6, and 2C were also recognized by anti-liver microsome and anti-liver/kidney microsome type 1 and type 2 autoantibodies, respectively. (2) Immunofluorescence and immunoperoxidase labeling of the plasma membrane was observed with the three auto-antibodies and with anti-cytochrome P-450 1A2, 2C, 2E1, or 3A4.


CONCLUSIONS
It is concluded that cytochromes P-450 are present and functional in the plasma membrane of human hepatocytes and that anti-cytochrome P-450 autoantibodies recognize epitopes expressed on the outer surface.
Loeper
J
J
Institut National de la Santé et de la Recherche Médicale: Unit 24, Clichy, France.
Descatoire
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Maurice
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Beaune
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Belghiti
J
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Houssin
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Ballet
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Feldmann
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Guengerich
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Pessayre
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D001323:Autoantibodies / Q000276:immunology*; D002462:Cell Membrane / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000276:immunology / Q000378:metabolism*; D000939:Epitopes; D005455:Fluorescent Antibody Technique; D006498:Hepatectomy; D006801:Humans; D015151:Immunoblotting; D007124:Immunoenzyme Techniques; D007668:Kidney / Q000276:immunology; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008861:Microsomes / Q000276:immunology; D008862:Microsomes, Liver / Q000276:immunology; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D010105:Oxygenases / Q000378:metabolism; D010477:Perfusion
D001323:Autoantibodies; D000939:Epitopes; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases; D009251:NADPH-Ferrihemoprotein Reductase