Characterization of growth hormone-releasing hormone stimulation of the endocrine pancreas: Studies with α- and β-adrenergic and cholinergic antagonists

Abstract. The 40 aminoacids residue of pancreatic growth hormone-releasing hormone stimulates the secretion of insulin, glucagon, an somatostatin from the pancreas. To determine whether this stimulation of islet hormone secretion is mediated via adrenergic or cholinergic receptor sites, we studied the effects of 30 nmol/l of the growth hormone-releasing hormone on the release of insulin, glucagon, and somatostatin in the presence of either α-adrenergic (phentolamine), β-adrenergic (propranolol) or cholinergic (atropine) blocking agents. The responses to the growth hormonereleasing hormone were not significantly modified by adrenergic or cholinergic blockers. The findings rule out an interaction with adrenergic and cholinergic receptors on islet cells. It is at present unknown whether the growth hormone-releasing hormone stimulates islet hormone secretion via an interaction with specific growth hormone-releasing hormone receptors or vasoactive intestinal peptide receptors.