Ellinger Isabella, Fuchs Renate
Department of Pathophysiology, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria.
J Biomed Biotechnol. 2010;2010:850320. doi: 10.1155/2010/850320. Epub 2010 Jan 27.
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.
辣根过氧化物酶（HRP）常被用作液相标记物来表征内吞和转胞吞过程。同样，它也被用于研究大鼠肝脏肝细胞中胆汁液体分泌的机制。然而，HRP含有甘露糖残基，因此会与包括肝细胞在内的肝细胞上的甘露糖受体（MRs）结合。为了研究MR介导的HRP转运的内吞作用在肝细胞中的作用，我们测定了寡糖甘露聚糖对离体灌注大鼠肝脏中HRP胆汁分泌的影响。施加1分钟的HRP脉冲，然后进行无标记灌注。HRP以双相动力学出现在胆汁中：标记后7分钟出现第一个峰值，15分钟出现第二个峰值。在存在两倍过量甘露聚糖的情况下，用0.8mg/mL HRP灌注可使第一个峰值降低41%，而对第二个峰值无影响。结合最近发表的关于大鼠肝细胞中MR表达的数据，这证明了HRP转胞吞的两种不同机制：一种快速的、受体介导的转运和一种较慢的液相转运。
