The sialic acid and carbohydrate content and the synthesis of glycoprotein from radioactive precursors by tissues of the normal and diseases upper intestinal tract

Binding of cationized ferritin to the cell-coat glycoproteins of human and rat small-intestinal absorptive cells

The binding of cationized ferritin (CF) to the cell-coat (glycocalyx) glycoproteins of human and rat intestinal absorptive cells was investigated in relation to the amount of sialic acid in these macromolecules. The cell coat of human absorptive cells exhibited poor binding of CF and contained a small amount of sialic acid. The cell coat of rat absorptive cells had about ten times more sialic acid than that of human cells and showed a strong affinity for the marker. The removal of sialic acid from the cell-coat glycoproteins of rat intestinal cells by neuraminidase treatment abolished CF binding. These results suggest that sialic acid is necessary for CF binding and that human and rat intestinal absorptive cells show a species-specific difference in the sugar composition of the cell coat.

The binding of a glycopeptide component of wheat gluten to intestinal mucosa of normal and coeliac human subjects

A carbohydrate-containing component of wheat gluten (glyc-gli) has been prepared which is toxic to coeliac intestinal mucosa. Its amino acid composition is uniquely different from that of the parent gluten and from alpha-gliadin. This glyc-gli material has been shown to bind to membrane components of the coeliac intestinal cell but to bind only poorly to normal intestinal cell membranes. Furthermore this binding can be interfered with by exogenous free carbohydrate suggesting that the toxic moiety of gluten acts in an analagous way to plant lectins. These data suggest that the underlying defect in coeliac disease is related to the composition of the surface membrane of the enterocyte.