A dose-response study of the effect of 0.1–5.0 μg kg^-1 h^-1 somatostatin was performed on food-induced rise of pancreatic polypeptide and insulin in 4 dogs. There was a dose-dependent suppression of the release of pancreatic polypeptide and insulin with an ED₅₀ of approximately 0.65 and 0.8 μg kg^-1 h^-1, respectively, during the first 45-min period. In the second 45-min period, high doses of somatostatin failed to suppress insulin concentrations whereas, the serum concentrations of pancreatic polypeptide were reduced by a similar degree as in the first 45 min. The differing effects of somatostatin on food-stimulated serum concentrations of insulin and pancreatic polypeptide indicate that somatostatin does not represent a uniform suppressor of pancreatic hormones.

MUe effect of 0.1, 0.4, 1.0, 2.0 and 5.0 micrograms kg-1 h-1 somatostatin on food-induced rise of serum gastrin concentrations was studied in 4 dogs. Whereas it has been shown previously that these doses of somatostatin reduce postprandial release of other gastroenteropancreatic hormones, there was no evidence of suppression of serum gastrin levels. A dose of 12.6 micrograms kg-1 h-1 somatostatin abolished the gastrin response completely. The study shows that low doses of somatostatin are not a uniform suppressor of gastroenteropancreatic hormones.