Effects of intravenous somatostatin and motilin on the blood glucose and hormonal response to oral glucose

. Exogenous intravenous infusions of control saline, somatostatin, motilin and somatostatin and motilin together were compared in normal volunteers for their effects on the rise of blood glucose following 50 g oral glucose and for their effects on gastric emptying and plasma hormone concentrations. All regulatory peptide infusions increased the rate of gastric emptying by between 182% and 198% at 60 min post-ingestion. The glucose response during the oral glucose tolerance test was suppressed when somatostatin with or without motilin was infused but was increased during motilin. The somatostatin infusion reduced concentrations of motilin, insulin, gastric inhibitory polypeptide, gastrin and neurotensin whilst the motilin infusion was associated with an increased initial rise in insulin and gastric inhibitory polypeptide. The metabolic effects of the motilin infusion were overriden by the effects of somatostatin when both peptides were infused together; this suggests that somatostatin inhibits both the effects and secretion of motilin.