Somatostatin. A regulatory modulator connecting nutrient entry and metabolism

Somatostatin is located in substantial quantities in the D-cells of the gastrointestinal tract and the endocrine pancreas. This unique tissue distribution supports the idea that somatostatin may be a factor that participates in the regulation of gastrointestinal and pancreatic functions as a common denominator for both local or paracrine and endocrine actions. This dual mechanism permits a local control of certain functions without necessarily affecting all potential target tissues at the same time, but it also provides the possibility to combine local effects with actions on more remote target organs. In the foregoing sections the present evidence for an endocrine role of somatostatin has been presented and the regulation and modulation of somatosatin release from the pancreas and stomach has been described. The release of somatostatin by ingested or absorbed nutrients as well as the tight connection to other neural and endocrine mechanisms known to participate in the handling of ingested and circulating nutrients strongly favors a role of somatostatin as a regulatory modulator connecting nutrient entry, primarily concerning gastrointestinal functions, and metabolism, concerning mainly the endocrine pancreas and the liver. Thus, somatostatin may respresent a major factor that integrates information from ongoing digestive and metabolic events, channelling this integrated information into the arterial plasma SLI concentration and providing a fine tuning of the rate at which certain nutrients enter the organism in balance with their rate of disposal, thus avoiding major perturbations of the homeostasis of the 'milieu interieur'.