Urotensin I

Urotensin I (Catostomus urotensin I), a CRF-like neuropeptide, acts as an agonist of CRF receptor with pEC₅₀s of 11.46, 9.36 and 9.85 for human CRF₁, human CRF₂ and rat CRF_2α receptors in CHO cells, and K_is of 0.4, 1.8, and 5.7 nM for hCRF₁, rCRF_2α and mCRF_2β receptors, respectively^[1][2]. IC50 & Target: pEC50: 11.46 (human CRF₁, CHO cells), 9.36 (human CRF₂, CHO cells), 9.85 (rat CRF_2α, CHO cells)^[1]
Ki: 0.4 nM (hCRF₁, cell assay), 1.8 nM (rCRF_2α, cell assay), and 5.7 nM (mCRF_2β, cell assay)^[2] In Vitro: Urotensin I is 2-3 times more potent than CRF or sauvagine in stimulating ACTH release from a superfused goldfish anterior pituitary cell column^[3].
Rat tail artery strips were incubated in the presence of 4 x 10(-3) M theophylline and Urotensin I (UI). At the concentrations of 1.50, 7.50 mU/ml but not of 0.75 mU/ml Urotensin I, the content of cAMP increased significantly^[4]. In Vivo: Intraperitoneal injections of urotensin I, a CRF-like neuropeptide isolated from the caudal neurosecretory system of the teleost Catostomus commersoni, ovine CRF and sauvagine all produced significant increases in circulating levels of plasma cortisol in goldfish in which endogenous ACTH secretion was suppressed with betamethasone^[3].