6agonist selectivity determinants in somatostatin receptor subtypes I and II.

The biological activities of the peptide hormone somatostatin are mediated through a recently identified family of G-protein-linked receptors. A number of somatostatin analogs have been characterized with selective affinities for particular somatostatin receptor subtypes. Using one such molecule (MK-678), we have delineated receptor regions that determine analog selectivity in the murine Type 1 and Type 2 somatostatin receptors. We find that the regions about the second and third extracellular loops of these two receptors contain the determinants for MK-678 selectivity and affinity.