Identification and characterization of binding sites for human urotensin-II in Sprague-Dawley rat renal medulla using quantitative receptor autoradiography.
Urotensin-II (U-II), a ligand for the G-protein-coupled receptor UT, has been characterized as the most potent mammalian vasoconstrictor identified to date. Although circulating levels of U-II are altered in lower species (e.g., fish) upon exposure to hypo-osmotic stress, little is known about the actions of this cyclic undecapeptide within the kidney, an organ that plays a pivotal role in the control of cardiovascular homeostasis, influencing both cardiac preload (plasma volume) and after load (peripheral resistance). The present study reports the identification of specific, high affinity [125I]hU-II binding sites in Sprague-Dawley rat kidney outer medulla by autoradiography and also through membrane radioligand binding (Kd 1.9 +/- 0.9 nM and Bmax 408 +/- 47 amol mm(-2) and Kd 1.4 +/- 0.3 nM and Bmax 51.3 +/- 7.8 fmol mg(-1) protein, respectively). Differences were observed in the binding characteristics within rat strains. Compared to the Sprague-Dawley, Wistar Kyoto (WKY) and spontaneously hypertensive (SHR) rat kidney outer medulla displayed low density < 20 fmol mg(-1) protein and low affinity (> 1 microM) [125I]hU-II binding sites. Thus, the relative contribution of specific U-II binding sites to the physiological actions of U-II in the control of cardiorenal homeostasis is worthy of further investigation.
Disa
Jyoti
J
Department of Vascular Biology and Thrombosis, Cardiovascular and Urogenital Center of Excellence for Drug Discovery, GlaxoSmithKline, 709 Swedeland Road, King of Prussia, PA 19406, USA.
Floyd
Latitia E
LE
Edwards
Richard M
RM
Douglas
Stephen A
SA
Aiyar
Nambi V
NV
D000818:Animals; D001345:Autoradiography; D001665:Binding Sites; D001667:Binding, Competitive; D006801:Humans; D007679:Kidney Medulla / Q000378:metabolism*; D007700:Kinetics; D008024:Ligands; D011485:Protein Binding; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D017207:Rats, Sprague-Dawley; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D013045:Species Specificity; D014579:Urotensins / Q000737:chemistry* / Q000378:metabolism
D008024:Ligands; D043562:Receptors, G-Protein-Coupled; D014579:Urotensins; C473142:Uts2r protein, rat; C029677:urotensin II