The ultrastructural localisation of De-Nol (colloidal tripotassium dicitrato-bismuthate--TDB) in the upper gastrointestinal tract of man and rodents following oral and instrumental administration.

In the presence of hydrochloric acid, tripotassium dicitrato-bismuthate forms a particulate precipitate which is electron dense. In upper gastrointestinal tract endoscopic biopsies, following a single oral dose, precipitate was detected between superficial oesophageal epithelial cells and also lining lipid droplets within oesophageal cells. The precipitate does not appear to penetrate the thick mucus barrier in the normal stomach but reaches the epithelial cell surface in the duodenum and proximal jejunum. Small particles of bismuth complex are endocytosed by the enterocyte and enter multivesicular bodies. A similar series of events was observed in rodents and an approximate time course for adsorption and endocytosis was estimated.