noun, plural: G cells
G cells are cells that secrete gastrin during digestion and in response to mechanical stress or high pH. Gastrin is a polypeptide hormone that promotes gastric juice secretion. The G cells are located mainly in the stomach, particularly in the pyloric antrum, and in the duodenum of the small intestine. They also occur in the pancreas.
During digestion, gastrin is released by the G cells into the bloodstream. The hormone binds to the cholycytoskinin B receptors. This activates the enterochromaffin-like cells to release histamine. It also induces the insertion of K+/H+ ATPase pumps into the apical membrane of parietal cells. This, in turn, stimulates the parietal cells to augment H+ release into the lumen of the stomach. As the pH in the stomach decreases, the secretion of gastrin eventually decreases. Gastrin also stimulates the smooth muscles of the stomach to augment their contractions. It also activates the pancreas and the gallbladder to secrete more pancreatic juice and bile, respectively.
G cells release gastrin in response to varying stimuli and one of them is by the signals coming from the vagus nerve. The distention of the stomach wall and the presence of amino acids during the digestion of proteins also stimulate the G cells to release gastrin.