title: Receptor-mediated and fluid-phase transcytosis of horseradish peroxidase across rat hepatocytes.
abstract: Horseradish peroxidase (HRP) is often used as a fluid-phase marker to characterize endocytic and transcytotic processes. Likewise, it has been applied to investigate the mechanisms of biliary secretion of fluid in rat liver hepatocytes. However, HRP contains mannose residues and thus binds to mannose receptors (MRs) on liver cells, including hepatocytes. To study the role of MR-mediated endocytosis of HRP transport in hepatocytes, we determined the influence of the oligosaccharid mannan on HRP biliary secretion in the isolated perfused rat liver. A 1-minute pulse of HRP was applied followed by marker-free perfusion. HRP appeared in bile with biphasic kinetics: a first peak at 7 minutes and a second peak at 15 minutes after labeling. Perfusion with 0.8 mg/mL HRP in the presence of a twofold excess of mannan reduced the first peak by 41% without effect on the second one. Together with recently published data on MR expression in rat hepatocytes this demonstrates two different mechanisms for HRP transcytosis: a rapid, receptor-mediated transport and a slower fluid-phase transport.
authors.affiliation: Department of Pathophysiology, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria.
authors.forename: Isabella
authors.initials: I
authors.lastname: Ellinger
authors.forename: Renate
authors.initials: R
authors.lastname: Fuchs
mesh_terms: D000818:Animals; D001212:Asialoglycoproteins / Q000378:metabolism; D001646:Bile / Q000378:metabolism; D015415:Biomarkers; D003911:Dextrans / Q000378:metabolism; D004705:Endocytosis; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives / Q000378:metabolism; D022781:Hepatocytes / Q000378:metabolism*; D006735:Horseradish Peroxidase / Q000378:metabolism*; D007700:Kinetics; D037181:Lectins, C-Type / Q000378:metabolism*; D008024:Ligands; D008297:Male; D008351:Mannans / Q000378:metabolism; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins / Q000378:metabolism*; D009961:Orosomucoid / Q000031:analogs & derivatives / Q000378:metabolism; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism*; D012212:Rheology; D015398:Signal Transduction
chemical_list: D001212:Asialoglycoproteins; D015415:Biomarkers; D003911:Dextrans; D037181:Lectins, C-Type; D008024:Ligands; D008351:Mannans; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D009961:Orosomucoid; D011956:Receptors, Cell Surface; C017030:asialoorosomucoid; C015219:fluorescein isothiocyanate dextran; D006735:Horseradish Peroxidase; D016650:Fluorescein-5-isothiocyanate