The role of Concanavalin A-binding fraction in cholesterol crystallization in native human bile

Abstract

Background/Aims: Many Concanavalin A-binding glycoproteins have been proposed to influence cholesterol crystallization in human bile. This has been studied mainly by addition of the Concanavalin A-binding fraction to model bile. The physiological relevance of the proteins in native bile is not yet known. The aim of this study was to establish the role of the Concanavalin A-binding fraction in cholesterol crystallization in native human gallbladder bile. Methods: To determine the effects of the removal of Concanavalin A-binding fraction, fresh human gallbladder bile was incubated with either Concanavalin A-Sepharose or Sepharose alone. Beads were sedimented and crystallization was studied in the supernatant. Results: Extraction of Concanavalin A-binding fraction decreased crystallization in fast-nucleating biles (Crystal Detection Time <-4 days). Slow-nucleating biles were not affected. The effect could not be related to the content of known pronucleating proteins (IgA, IgM, haptoglobin, aminopeptidase N and α1-acid-glycoprotein), since the slow-nucleating biles contained similar amounts of these proteins. Conclusions: Although Concanavalin A-binding fraction always accelerated crystallization when added to model bile, removal of the same fraction from native bile often had no effect. We conclude that slow-nucleating biles in particular contain undertermined factors which regulate the activity of pronucleators.