AGONIST SELECTIVITY DETERMINANTS IN SOMATOSTATIN RECEPTOR SUBTYPE-I AND SUBTYPE-II

The biological activities of the peptide hormone somatostatin are medi ated through a recently identified family of G-protein-linked receptor s. A number of somatostatin analogs have been characterized with selec tive affinities for particular somatostatin receptor subtypes. Using o ne such molecule (MK-678), we have delineated receptor regions that de termine analog selectivity in the murine Type 1 and Type 2 somatostati n receptors. We find that the regions about the second and third extra cellular loops of these two receptors contain the determinants for MK- 678 selectivity and affinity