[Demonstration of a specific receptor site for glucagon-37 (oxyntomodulin/bioactive enteroglucagon) in rat oxyntic...

In this work, we show directly the existence of specific binding sites for Glucagon-37 (G-37) in isolated oxyntic glands from rat fundic mucosa. The binding of 125I-Glucagon-37 was inhibited by G-37 with a dissociation constant KD = 2.6 X 10(-9) M (high affinity binding capacity = 85 fmol/mg of protein) and by pancreatic Glucagon (G-29) with a KD = 2.2 X 10(-8) M. These results confirm the tissue specificity of G-37, evidenced in vitro on the cyclic AMP production by the same glands and in vivo on the inhibition of gastric acid secretion. They suggest that these activities are related to the G-37-binding on this novel receptor site for Glucagon-related peptides, which is distinct from receptors for the main stimulants of acid secretion, such as Gastrin, Histamine or cholinergic agents.