In vitro and in vivo pharmacological characterization of the novel UT receptor ligand [Pen5,DTrp7,Dab8]urotensin II(4-11) (UFP-803).
The novel urotensin-II (U-II) receptor (UT) ligand, [Pen(5),DTrp(7),Dab(8)]U-II(4-11) (UFP-803), was pharmacologically evaluated and compared with urantide in in vitro and in vivo assays. In the rat isolated aorta, UFP-803 was inactive alone but, concentration dependently, displaced the contractile response to U-II to the right, revealing a competitive type of antagonism and a pA(2) value of 7.46. In the FLIPR [Ca(2+)](i) assay, performed at room temperature in HEK293(hUT) and HEK293(rUT) cells, U-II increased [Ca(2+)](i) with pEC(50) values of 8.11 and 8.48. Urantide and UFP-803 were inactive as agonists, but antagonized the actions of U-II by reducing, in a concentration-dependent manner, the agonist maximal effects with apparent pK(B) values in the range of 8.45-9.05. In a separate series of experiments performed at 37 degrees C using a cuvette-based [Ca(2+)](i) assay and CHO(hUT) cells, urantide mimicked the [Ca(2+)](i) stimulatory effect of U-II with an intrinsic activity (alpha) of 0.80, while UFP-803 displayed a small (alpha=0.21) but consistent residual agonist activity. When the same experiments were repeated at 22 degrees C (a temperature similar to that in FLIPR experiments), urantide displayed a very small intrinsic activity (alpha=0.11) and UFP-803 was completely inactive as an agonist. In vivo in mice, UFP-803 (10 nmol kg(-1)) antagonized U-II (1 nmol kg(-1))-induced increase in plasma extravasation in various vascular beds, while being inactive alone. In conclusion, UFP-803 is a potent UT receptor ligand which displays competitive/noncompetitive antagonist behavior depending on the assay. While UFP-803 is less potent than urantide, it displayed reduced residual agonist activity and as such may be a useful pharmacological tool.
Camarda
Valeria
V
Department of Experimental and Clinical Medicine, Section of Pharmacology, University of Ferrara, Ferrara, Italy.
Spagnol
Martina
M
Song
Wei
W
Vergura
Raffaella
R
Roth
Adelheid L
AL
Thompson
Jonathan P
JP
Rowbotham
David J
DJ
Guerrini
Remo
R
Marzola
Erika
E
Salvadori
Severo
S
Cavanni
Paolo
P
Regoli
Domenico
D
Douglas
Stephen A
SA
Lambert
David G
DG
Calò
Girolamo
G
D000818:Animals; D001011:Aorta / Q000187:drug effects; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D008024:Ligands; D051379:Mice; D010446:Peptide Fragments / Q000494:pharmacology*; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D014579:Urotensins / Q000494:pharmacology*
D008024:Ligands; D010446:Peptide Fragments; D043562:Receptors, G-Protein-Coupled; D014579:Urotensins; C473142:Uts2r protein, rat; C512325:urotensin II receptor, mouse; C029677:urotensin II