The turnover of mucin glycoprotein in the stomach

It is proposed that the gastric mucosa, during early stages of fasting, accumulates secreted mucin on the luminal surface of the tissue. The accumulated mucin is subsequently released from its adherent state, on precipitation by freshly secreted acid from the stimulated parietal cells, or, as an alternate mechanism, simply by the passage of ingested food. The gastric mucosa on stimulation by ulcerogenic aspirin, on the other hand, responds immediately to the insult by rapid shedding of its adherent mucin, then, within 5 minutes by an almost complete shut-down of respiration and biosynthesis, not only of glycoproteins but also of proteins and nucleic acids. However, oxygen consumption and biosynthesis quickly revive, in an endeavour to restore the mucosal tissue which has survived, with the result that the turnover of intracellular contents is augmented very much more than its normal rapid rate, illustrated in the gastric epithelial cell by Bennett in 1971 and in the non-secreting duodenal columnar cell by Bennett and Leblond (1970). 14C-Fucose was found in the Golgi apparatus, 2 minutes after injection into the animal, while within 20 minutes it had reached the surface membranes before extrusion.