Assessment of mucus glycoprotein erosion by measurement of sialic acid in gastric secretions: pathophysiologic and therapeutic aspects.

The quantification of mucus glycoproteins (GPs) faces paramount difficulties in terms of methods and interpretation. Mucus glycoprotein erosion, however, might be quantified in gastric juice by measurement of GP-bound sialic acid. Basal sialic acid content was low in normal healthy subjects (N) and in nonulcer dyspepsia (NUD) patients. They were five to six times higher in duodenal ulcer (DU), or more in Zollinger-Ellison patients. Pentagastrin stimulation induced a five- to sixfold rise in N and NUD patients although it did not affect DU patient sialic acid contents. Relationships between sialic acid content and pepsin output in DU indicate that pepsin exerts a variable mucolytic activity depending on disease evolution. In addition to pepsin, duodenogastric reflux exerts a potent mucolytic effect. Therapeutically, highly selective vagotomy without recurrent ulcer markedly reduced mucus erosion. The reduction of mucus erosion by protective drugs has been observed in some cases but in other cases sialic acid measurement did not allow to verify a protective effect. Adherent mucus analysis by high-performance liquid chromatography (HPLC) should allow one to appreciate GP fractions qualitatively. Combination of both methods should allow further determination of the mucus protective role, simultaneously investigating the adherent mucus quality and eroded GPs.