Demonstration of a cytochemical difference between the tubulovesicles and plasmalemma of gastric parietal cells by ATPase and NPPase reactions.

Pieces of rat and human gastric mucosa were fixed in glutaraldehyde and paraformaldehyde and were processed by the methods of Wachstein-Meisel and of Ernst for the cytochemical demonstration of adenosine triphosphatase (ATPase) and p-nitrophenylphosphatase (NPPase) respectively. Electron microscopic examination of reacted sections revealed the ATPase reaction to be localized to the plasmalemma and to mitochondrial cristae and the NPPase reaction to the plasmalemma. The tubulovesicles were unreactive. By thus demonstrating a cytochemical difference between the plasmalemma and tubulovesicle membrane, this study suggests that the tubulovesicles do not represent an extension of or reserve of mature plasmalemma. If the tubulovesicles represent a reserve of membrane that can be rapidly utilized to expand the plasmalemma, then these studies suggest that additional membrane constituents are added, activated, or unmasked in the process.