Somatostatin Cell Processes as Pathways for Paracrine Secretion

Abstract

Somatostatin is produced by gastrointestinal endocrine cells that have long, nonluminal, cytoplasmic processes. Such processes terminate on other cell types, including gastrin-producing and hydrochloric acid-producing cells, whose functions are profoundly affected by somatostatin. The findings suggest that somatostatin cells control the functions of other cells through local release of the peptide by way of cytoplasmic processes. Also, certain other types of gastrointestinal endocrine cells have similar cytoplasmic prolongations, which may have analogous local (paracrine) regulatory functions.

The relative frequency and topographical distribution of somatostatin-, GRP-,APP-, glucagon-,5-HT-, and neurotensin-immunoreactive cells in the proventriculus of seven species of birds.

“…These morphological features support the concept that many of the proventricular endocrine cells may function as mechanoreceptors and respond to mechanical stimuli such as pressure or tension caused by foods (KUSUMOTO et al, 1979;LARSSON et al, 1979;YAMADA et al, 1979). Somatostatin-immunoreactive cells in particular may function as mechanoreceptors as well as typical paracrine cells as reported in mammalian fundic glands (ALUMETS et al, 1979;KUSUMOTO et al, 1979;LARSSON et al, 1979).…”

“…These morphological features support the concept that many of the proventricular endocrine cells may function as mechanoreceptors and respond to mechanical stimuli such as pressure or tension caused by foods (KUSUMOTO et al, 1979;LARSSON et al, 1979;YAMADA et al, 1979). Somatostatin-immunoreactive cells in particular may function as mechanoreceptors as well as typical paracrine cells as reported in mammalian fundic glands (ALUMETS et al, 1979;KUSUMOTO et al, 1979;LARSSON et al, 1979). It is well established that somatostatin suppresses the secretion of endocrine as well as exocrine cells (PATEL et al, 1981) and that GRP (or bombesin) stimulates both directly and indirectly (via gastrin cells) gastric acid secretion by oxyntic cells (VARNER et al, 1981).…”

Effect of the somatostatin analog octreotide on gastric mucosal function and histology during 3 months of preoperative treatment in patients with acromegaly

“…Other effects of octreotide on intragastric acidity are therefore likely to play a role. They probably include somatostatin receptor subtype-2 (SSTR-2)-mediated inhibition of histamine release from the enterochromaffin-like cells (ECL cells) (28)(29)(30)(31)(32) and/ or a direct inhibition of the acid-secreting parietal cells (33)(34)(35). Interestingly, intragastric acidity was quickly restored, as previously observed by Londong et al (17), despite an increase in the octreotide dose and in the presence of a continuously low gastrin concentration.…”

Localization of peptide YY (PYY) in gastrointestinal endocrine cells and effects on intestinal blood flow and motility.

“…The localization of PYY in mucosal endocrine cells with an apical end reaching the lumen suggests that intraluminal contents can trigger the release of PYY and that PYY may have a paracrine or hormonal action. A paracrine action is further suggested by the fact that the PYY cells sometimes have long processes resembling those of somatostatin-immunoreactive cells in the stomach (13). The present findings suggest that a local PYY release would lead to, for example, a decrease in blood supply and colonic smooth muscle tone.…”