In recent years, several studies have demonstrated that urotensin II (UII) and urotensin II-related peptide (URP) can exhibit differential biological activity. So far, known antagonists of the urotensin II receptor (UT) are of limited usefulness for investigating the specific pathophysiological role of UII or URP. Therefore, identification of new compounds able to discriminate UII- and URP-associated biological activities is crucially needed. In the present study, we report preliminary data regarding the pharmacological properties of a novel UT ligand termed urocontrin, i.e. [Bip(4)]URP, that is able to reduce the ex vivo efficacy of hUII- but not URP-induced vasoconstriction in rat aortic rings. In vivo studies support the pharmacological profile described above. Although urocontrin exert some residual agonist activity, this compound should be useful for the rational design of potent molecules that would allow discriminating specific biological action mediated by UII or URP.
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