Glucagon receptor antagonist (pA2 = 7.2 for inhibition of glucagon-induced adenylyl cyclase activation in rat liver membranes); displays no agonist activity. Enhances glucose-stimulated pancreatic insulin release in vitro. Blocks added glucagon-induced hyperglycemia in normal rabbits without affecting glycogenolysis in vivo. Also blocks endogenous glucagon-induced hyperglycemia in streptozocin diabetic rats. MW (observed): 3358.68.