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Correction for vol. 47, p. 72

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An error occurred in abstract P98 (Gut 2000;47(Suppl III):A72). The correct abstract is published here.

P98

AN INVESTIGATION INTO THE IMPACT OF ALGINATES AND EPIDERMAL GROWTH FACTOR ON ENDOCYTOSIS-A STUDY IN FOUR OESOPHAGEAL CELL LINES

P.M. McPherson1, P.E. Ross1, P.W. Dettmar2.Gastroenterology Research Laboratory, Molecular and Cellular Pathology, University of Dundee. 2Reckitt Benckiser Healthcare (UK) Ltd, Hull, UK.

Introduction:Endocytosis is a process whereby eukaryotic cells take up extracellular material by a variety of different mechanisms. These endocytic functions are of great importance and are involved in the regulation of cell surface receptor expression, maintenance of cell polarity, cholesterol homeostasis and a host of other physiologcal processes. In this investigation we looked specifically at fluid phase endocytosis and the impact alginates and epidermal growth factor (EGF) have on this activity.

Background: Alginates are extracted from seaweed with their structure and properties related to the species of seaweed. They are carbohydrate polymers made up of D-mannuronic (M block) and L-guluronic (G block) acid residues, and may also be made up of sequences of mixed residues (MG blocks). These carbohydrate polymers appear to promote migration and restitution in gastrointestinal epithelial cells in vitro and in vivo by modulating the expression and functional activity of cell junctional proteins such as the E-cadherin-catenin complex. EGF is a 6kd polypeptide that has a role in tissue repair, cell proliferation, ulcer healing and cell migration. EGF also inhibits acid production and imparts a cytoprotective mechanism protecting the oesophageal mucosa from gastric refluxate. Similar biological effects have been recognised with alginates that are used extensively in medications to alleviate symptoms associated with gastric reflux

Methods: In this study we have used four oesophageal carcinoma cell lines, 2 squamous cell carcinomas and two adenocarcinomas. Cells were incubated with combinations of fluorescent microspheres (0.02μm), alginate and EGF for 1 hour, and then analysed by FACScan®. Alginates were used at a concentration of 2mg/ml and EGF at 10ng/ml.

Results:

  • All alginates used in this study up-regulate fluid phase endocytosis.

  • EGF up-regulates endocytosis.

  • Incubation with EGF and alginate up regulates fluid phase endocytosis.

  • Levels of up-regulation varied depending on alginate used.

  • Alginates up-regulate fluid phase endocytosis more than physiological levels of EGF.

Conclusions: We have shown that both alginates and EGF up-regulate fluid phase endocytosis in all cell lines used in this study. However alginates up-regulate this process significantly whereas EGF does not. The mechanism for this alginate action is not yet identified, but it is possible that alginates interact with the receptor for EGF.

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