This is done both directly on the parietal cell and indirectly via binding onto CCK2/gastrin receptors on ECL cells in the stomach, which then responds by releasing histamine, which in turn acts in a paracrine manner on parietal cells stimulating them to secrete H+ ions. The presence of gastrin stimulates parietal cells of the stomach to secrete hydrochloric acid (HCl)/gastric acid. Note: this diagram does not illustrate gastrin's stimulatory effect on ECL cells. G cell is visible near bottom left, and gastrin is labeled as the two black arrows leading from it.
Gastrin binds to cholecystokinin B receptors to stimulate the release of histamines in enterochromaffin-like cells, and it induces the insertion of K +/H + ATPase pumps into the apical membrane of parietal cells (which in turn increases H + release into the stomach cavity). It is released by G cells in the pyloric antrum of the stomach, duodenum, and the pancreas. Gastrin is a peptide hormone that stimulates secretion of gastric acid (HCl) by the parietal cells of the stomach and aids in gastric motility.