A B S T R A C T Cyclic somatostatin was administered intravenously (10 ,ug/min for 60 min) to 10 healthy overnight fasted (postabsorptive) subjects and to 5 healthy 60-h fasted subjects. In both groups, arterial insulin and glucagon fell 50%o and splanchnic release of these hormones was inhibited. In the overnight fasted subjects splanchnic glucose output fell 70%, splanchnic uptake of lactate and pyruvate was unchanged, alanine uptake fell by 25%, and glycerol uptake rose more than twofold in parallel with an increase in arterial glycerol.In the 60-h fasted group splanchnic glucose output was less than 40%o of that observed in the overnight fasted subjects. Somatostatin led to a further decrease (-70%) in glucose production. Splanchnic uptake of lactate and pyruvate fell by 30-40%o, amino acid uptake was unchanged, while uptake of glycerol rose fivefold. Total uptake of glucose precursors thus exceeded the simultaneous glucose output by more than 200%o. Splanchnic uptake of FFA rose fourfold during somatostatin while output of beta-hydroxybutyrate increased by 75%. Estimated hepatic blood flow fell 25-35% and returned to base line as soon as the somatostatin infusion ended.It is concluded that (a) somatostatin-induced hypoglucagonemia results in inhibition of splanchnic Dr. Felig is the recipient ofa Research Career Devleopment Award