Mechanism of sucrose uptake by isolated rat hepatocytes

✍ Scribed by Dr. Anna W. Sasaki; Stuart K. Williams; Mahendra Jain; Roger C. Wagner

• Publisher: John Wiley and Sons
• Year: 1987
• Tongue: English
• Weight: 616 KB
• Volume: 133
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041330123

✦ Synopsis

The transport of molecules by nonspecific endocytosis has been described in many cell types, but it has not been characterized in hepatocytes. Because of its central role in the clearance of solutes from portal blood, endocytosis might represent a significant mode of cellular transport. We investigated the mechanism of sucrose uptake in an isolated hepatocyte system. Liver cells were isolated by perfusion and collagenization of rat liver, followed by differential centrifugation. Hepatocytes were then incubated with 14C-sucrose and harvested by spinning through oil in microfuge tubes. Radioactivity was standardized against DNA content. We found that sucrose uptake is concentration-dependent from 5 pM to 100 mM and follows first-order kinetics. Washout studies indicate that exocytosis is responsible for the dynamic equilibrium reached. Arrhenius analysis of temperature dependence yields a linear plot (E, = 14.2 KcaVmol). In addition, sucrose uptake is independent of cellular ATP levels. We conclude that sucrose is transported by fluid-phase micropinocytosis in isolated hepatocytes and that this transport mechanism may be important in the uptake of diverse molecules into liver cells.

Methods

Formula 963 and 14C-sucrose were obtained from New England Nuclear, Inc. (Billerica, MA). Sucrose purity of > 99% was confirmed by paper chromatography (Smith, 1960) followed by analysis on a Searle Actigraph 111 strip