Dose-response effect of somatostatin-14 on human basal pancreatic hormones

The effect of increased doses of Somatostatin-14 (3,10, 30,100, 300 μg/h) on basal release of insulin, pancreatic glucagon and pancreatic polypeptide (PP) was investigated on eight normal volunteers. Levels of Somatostatinlike immunoreactivity (SLI) was determined in order to correlate the increased SLI levels with the degree of islet hormone inhibition (r = 0.9947, p <0.01). By increasing the basal levels of SLI by one-third, a significant inhibition (p <0.01) of insulin, glucagon, and PP was noted (78.5, 78.6, 75.2%, respectively, on basal levels). The maximal effect was obtained with 300 μg/h for insulin, with 30 μg/h for glucagon and 100 μg/h for PP. In evaluating the relative inhibitory potency of somatostatin, expressed as ED₅₀, the theoretic potency of somatostatin on each peptide had similar values, ranging from 30 to 10 μg/h. The present data show that a minimal peripheric increase in SLI is able to regulate basal islet pancreatic hormones.