ABSTRACT
Somatostatin (SST) was originally discovered as a hypothalamic peptide which inhibits growth hormone (GH) secretion from the pituitary gland. It appears in two molecular forms, composed o f 14 or 28 amino-acid residues. Moreover, another family of peptides, called cortistatins (CST), was described. CST are encoded by a different gene, but they share partly the structure of SST and bind to SST receptors. Further studies revealed that SST is expressed not only in the hypothalamus but is widely distributed in central and periph eral nervous systems as well as in nonneural peripheral tissues, mainly in the gut. SST is now known to exert a large spectrum of functions, mostly of an inhibitory nature. It inhibits the secretion of hormones, like GH and thyrotropin (TSH), neuro-enterohormones like gastrin, cholecystokinin, vasoactive intestinal peptide (VIP), gastric inhibitory polypeptide (GIP), mo tilin, secretin, pancreatic polypeptide and glucagon-like peptides (GLP), and exocrine se cretions. SST modulates the functions of nervous and immune systems and exerts a direct antiproliferative effect on cell and tissue growth. Because of a very short half-life (approx. 60 seconds) the therapeutic application of exogenous SST is limited. To overcome this obstacle, the long-acting analogs of SST were synthesized.
