Somatostatin receptor SSTR

In comparison tvith the agonist analogues, very few antagonists of somatostatin have been obtained by amino acid substitution. Two octapeptide derivatives, 4-NO2-Phe-c(D-Cys-Tyr-D-Trp-Lys-Thr-Cys)-Tyr-NHj and Ac-4-NO2-Phe-c(D-Cys-Tyr-D-Trp-Lys-Thr-Cys)-D-Tyr-NHj (inactive at the SST, and SST receptor subtypes high affinity for the SSTRj and SSTR receptor subtypes) inhibited somatostatin-mediated inhibition of cAMP accumulation in a dose-dependent manner. The more potent antagonist, Ac-4-NO2-Phe-c(D-Cys-Tyr-D-Trp-Lys-Thr-Cys)-D-Tyr-NHj], displays a binding affinity to SSTRj comparable with that observed for the native hormone. H-Nal-c[D-Cys-Pal-D-Trp-Lys-Val-Cys]-Nal-NHj was also a more selective hSSTRj antagonist. 

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