The effect of acid-stimulating and inhibiting drugs on the ultrastructure of gastric parietal cells in man.

The ultrastructure of the human parietal cell at rest, after stimulation of gastric acid secretion by pentagastrin and after inhibition with propantheline or cimetidine, an H2-receptor antagonist, was studied. On stimulation there was an increase in the total secretory surface area of the gastric gland and canaliculus, with a concomitant decrease in the tubulovesicular system. On inhibition there was a decrease in the secretory surface area and a corresponding increase in the tubulovesicular system. These results are in agreement with other reports and support the hypothesis that during secretion of acid the tubulovesicular system increases the secretory surface by eversion or fusion of the vesicles and tubules with the plasmalemma. On inhibition there is thought to be reformation of the tubulovesicular system by pinocytosis. There is also ultrastructural evidence for the theory of membrane flow between the tubulovesicular system and the microvilli of the canaliculus and gastric lumen. Furthermore, there was an increase in lysosomal activity after the administration of the inhibiting drugs. It is suggested that the increased lysosomal activity could be involved in reducing the quantity of membrane after the membrane flow which occurs on gastric acid inhibition.