Electron microscopic evidence for epidermal growth factor receptor (EGF-R)-like immunoreactivity associated with the basolateral surface of gastric parietal cells.

Epidermal growth factor (EGF), in addition to its effects on cell growth, has a suppressive effect on gastric hydrochloride secretion. We recently demonstrated EGF-receptor (EGF-R)-like immunoreactivity on human gastric parietal cells by light microscopy. To reveal further the localization of this reaction an immuno-electron microscopical study was performed. 528IgG, an anti-EGF-R murine monoclonal antibody and a polyclonal anti-EGF antibody were employed for immunostaining using the avidin-biotin method. Positive reaction against 528IgG was shown mostly on the outer membrane of parietal cells, except in the apical portion. No reaction was observed on most of the intracytoplasmic membranes including intracellular canaliculi, endoplasmic reticulum and other membranous components. In the basillar portion, the 528IgG-positive parietal cell membrane formed labyrinthine interdigitations. No reaction against anti-EGF was demonstrated in any of the gastric mucosal cells, although a reaction was clearly shown on salivary gland cells. These findings suggest a blood-mediated direct action of EGF on parietal cells.