Localization of phospholipid-rich zones in rat gastric mucosa: possible origin of a protective hydrophobic luminal lining.

Mammalian gastric mucosa is unusually hydrophobic or nonwettable, which may be an essential biophysical characteristic of the gastric mucosal barrier. Since this property may be attributable to an adsorbed layer of surface-active phospholipids (SAPL), we investigated the distribution of SAPL in rat oxyntic mucosa. Ferric hematoxylin (FH) and iodoplatinate (IP), selective histochemical stains for phospholipids (as confirmed by spot tests), were used to detect SAPL in frozen sections and aldehyde-fixed tissue, respectively. Using FH staining in conjunction with extraction procedures that either solvate or preserve SAPL, we determined that positive reactivity was the greatest in the apical third of the oxyntic mucosa between the glandular neck region and the surface. IP reactivity appeared to parallel the FH staining pattern. Mucous cells, especially the surface epithelial cells, were heavily stained. Electron microscopic examination revealed that these cells contain inclusion bodies associated with various subcellular organelles, e.g., nuclear envelope, endoplasmic reticulum, Golgi apparatus and its vesicles, and mucous secretory granules. Vesicles and myelin figures, which resembled those found in lung surfactant, were observed extracellularly in close association with the surface mucous cells. Our findings suggest that mucous cells are actively involved in synthesis and storage of SAPL, which may be an essential component of the stomach's protective hydrophobic lining.