Effects of atropine on GIP-induced insulin and pancreatic polypeptide release in man.

Eight fasting students were given an infusion of porcine gastric inhibitory polypeptide (GIP) and glucose with or without atropine on two separate days. Mean serum insulin levels increased significantly and similarly on both occasions, indicating that both the glucose- and GIP-induced insulin release is unaffected by atropine. Plasma pancreatic polypeptide (PP) rose significantly during the GIP infusion on the day without atropine, suggesting a role for GIP in the intestinal phase of the PP release.