Involvement of somatostatin receptor subtypes in membrane ion channel modification by somatostatin in pituitary somatotropes

Clin Exp Pharmacol Physiol. 2007 Dec;34(12):1221-7. doi: 10.1111/j.1440-1681.2007.04806.x. Epub 2007 Sep 25.

Abstract

1. Growth hormone (GH) secretion from pituitary somatotropes is mainly regulated by two hypothalamic hormones, GH-releasing hormone (GHRH) and somatotrophin releasing inhibitory factor (SRIF). 2. Somatotrophin releasing inhibitory factor inhibits GH secretion via activation of specific membrane receptors, somatostatin receptors (SSTRs) and signalling transduction systems in somatotropes. 3. Five subtypes of SSTRs, namely SSTR1, 2, 3, 4 and 5, have been identified, with the SSTR2 subtype divided into SSTR2A and SSTR2B. All SSTRs are G-protein-coupled receptors. 4. Voltage-gated Ca(2+) and K(+) channels on the somatotrope membrane play an important role in regulating GH secretion and SRIF modifies both channels to reduce intracellular free Ca(2+) concentration and GH secretion. 5. Using specific SSTR subtype-specific agonists, it has been found that reduction in Ca(2+) currents by SRIF is mediated by SSTR2 and an increase in K(+) currents is mediated by both SSTR2 and SSTR4 in rat somatotropes.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Humans
  • Ion Channels / metabolism*
  • Pituitary Gland / cytology
  • Pituitary Gland / metabolism
  • Receptors, Somatostatin / metabolism*
  • Somatostatin / metabolism*
  • Somatotrophs / metabolism*

Substances

  • Ion Channels
  • Receptors, Somatostatin
  • Somatostatin