Is GIP a glucagon cell constituent?

"Gastric inhibitory peptide" or "glucose-dependent insulin-releasing peptide" (GIP) is a member of the gut hormone family. Its physiological action is thought to be related to its insulinotrophic effect. The occurrence and distribution of GIP was studied by immunohistochemistry. In all species examined including man, GIP immunoreactivity was found to reside in the glucagon cells of the pancrease and gut. Three pancreatic glucagonomas were found to contain numerous cells displaying GIP and glucagon immunoreactivity. The GIP antiserum used did not cross react with either pancreatic-type or gut-type glucagon (GLI).