Quantitative ultrastructural studies on gastric parietal cells.

Gastric biopsies were taken from dogs at three different functional states, namely, before histamine stimulation, during maximal histamine stimulation, and 1 hr after histamine infusion. Morphometric data were obtained from these three functional states by measuring, in electron micrographs, randomly selected parietal cells. In the unstimulated dogs, the area of the secretory surface amounted to about 0.19 m2 per cm3 of parietal cell mass. In the stimulated dogs, this area had increased to about 1.92 m2 per cm3. The surface membrane of the cytoplasmic tubulovesicles was reduced from 5.73 to 2.58 m2 per cm3 as a result of the histamine stimulation. One hour after stopping the histamine infusion, the parietal cells were similar in appearance to those from the unstimulated dogs. The data support the theory that the tubulovesicular membrane is incorporated into the secretory membrane as a result of the stimulation. The production of acid probably takes place mainly at the secretory surface.