ABSTRACT
Somatostatin (SST) exerts diverse biological effects acting through specific membrane receptors belonging to the family of G protein coupled receptors. So far five SST receptor subtypes (ssti.5) have been cloned and characterized. The genes for these receptor subtypes are localized on different chromosomes and are intronless, with one exception concern ing sst2, which exists in two forms (sst2A> sst2ß)· Native SST existing mainly in two molecular forms (14 or 28 amino acid peptide) binds to all five sst subtypes with high nanomolar affinity, however some minor differences exist. The commercially available SST analogs (octreotide and lanreotide) bind only with high affinity to sst2 and sstş. Based on the binding studies with different SST analogs the family of SST receptors was divided into two subclasses. Subtype 1 and 4 of sst create one subclass and react poorly with these analogs, whereas sst2,3 and sstş bind these analogs with high affinity comparable to that of native SST.
