Somatostatin (SRIF) is a 14 amino-acid-containing peptide primarily expressed in the hypothalamus. It is a major physiological regulator of growth hormone (GH) secretion and is critical in maintaining the pulsatile release of GH. SRIF induces its biological effects by interacting with membrane-associated receptors, of which a family of five have recently been cloned. The cloned receptor subtype referred to as sstr2 may have an important role in mediating the inhibitory effects of SRIF on GH secretion. This is suggested from pharmacological studies showing that a large series of SRIF analogs, including the clinically used peptides octreotide and lantreotide, had a similar rank order of affinities for binding to sstr2 and to inhibit GH secretion. Stimulation of sstr2 may lead to inhibition of Ca2+ influx into somatotrophs to reduce GH secretion. Structural analysis of the cloned sstr2 has revealed binding domains of the receptor that may be useful in the development of antagonists and nonpeptide agonists at this receptor, which could have clinical uses in the regulation of GH secretion and other biological functions of SRIF.
From: Human Growth Hormone: Research and Clinical Practice Edited by: R. G. Smith and M. O. Thorner © Humana Press Inc., Totowa, NJ
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