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The influence of somatostatin (a bolus injection of 250 micrograms i.v. followed by 6 micrograms/min for 40 min) on the plasma cyclic AMP, insulin, glucose and non-esterified fatty acid (NEFA) responses to i.v. adrenaline (0.07 micrograms/kg body-weight/min for 20 min) and the plasma cyclic AMP, insulin and glucose responses to a bolus injection of i.v. glucagon (0.01 mg/kg BW) were studied in normal subjects. Somatostatin suppressed the insulin response to glucagon and inhibited the insulin rebound observed on termination of adrenaline infusion. The plasma glucose response to glucagon was exaggerated by somatostatin, reflecting insulin deficiency. Neither the plasma glucose or plasma non-esterified fatty acid responses to adrenaline were influenced by somatostatin. Adrenaline produced a three-fold and glucagon a twenty-fold rise in plasma cyclic AMP and 15 min. This was not influenced by concurrent somatostatin infusion, indicating that somatostatin is not a universal inhibitor of hormone stimulated adenylate cyclase activity. This is supported by the failure of somatostatin to inhibit the metabolic actions of glucagon and adrenaline thought to be mediated by cyclic AMP.

The growth-hormone-release-inhibiting hormone somatostatin was infused in seven juvenile diabetic subjects during an arginine infusion test and in six juvenile diabetic subjects during an L-dopa stimulation test. The plasma growth hormone response to arginine and L-dopa was completely inhibited by somatostatin. The plasma pancreatic glucagon response to arginine was also inhibited by somatostatin. The plasma pancreatic glucagon level was not changed by L-dopa, but somatostatin induced a significant fall in this level. The plasma glucose increase after arginine and L-dopa administration was slightly inhibited by somatostatin. The arginine-induced fall in free fatty acids was prevented by somatostatin, and the L-dopa-induced rise in free fatty acids was enhanced by somatostatin. The growth hormone- and glucagon-surppressive effect of somatostatin may prove useful in controlling the metabolic state and in preventing the development of angiopathy in diabetic patients. A somatostatin preparation with prolonged activity is needed for lifelong administration, but the presently available compound may be of value as an adjunct in the standard treatment of diabetic ketoacidosis and coma.

Somatostatin was infused in various doses into normal subjects and juvenile diabetics for a 24-hour period preceded by a 24-hour control period and followed by another three-hour control period. Saline was infused during the first control period. Meals were served during the two 24-hour periods. Blood samples were taken hourly. Five normal males received a total dose of 4 mg. somatostatin. Four male diabetics received 2 mg., four received 4 mg., and four 6 mg. In the diabetics, somatostatin suppressed plasma growth hormone, glucagon, and glucose throughout the infusion. All parameters rebounded at cessation of infusion. In the normals, somatostatin suppressed plasma growth hormone, glucagon, and insulin but increased plasma glucose. It is concluded that the plasma glucose suppression in the diabetics is mainly due to the suppression of the diabetogenic hormones growth hormone and glucagon. A minor effect of decreased and/or delayed absorption of carbohydrates cannot be excluded in these experiments. The elevated plasma glucose levels in normals must be due to the suppressive effects of somatostatin on insulin secretion.