Gastrin-1 is also referred to as Gastrin-17 or “Little Gastrin.” Secretion of gastrin is induced by food intake and causes the release of gastric acid in the stomach. Secreted by the G cells in the gastric mucosa, it is one of the major bioactive forms of gastrin found in tissue and plasma (the other bioactive form is Gastrin-34 or Big Gastrin). Both Gastrin-17 and Gastrin-34 are carboxy-amidated and partially tyrosine sulfated. Binding of Gastrin to the CCK2/gastrin receptor requires carboxy-amidation, however sulfation is not necessary for binding to the receptor. Binding of Gastrin to the CCK2/Gastrin receptors on parietal cells of the stomach causes them to secrete hydrochloric acid (HCl) and stimulates lectin-like protein Reg expression via activation of PKC and RhoA. Gastrin also plays a role in release of Histamine and Pepsinogen.