Identification and characterization of binding sites for human urotensin-II in Sprague-Dawley rat renal medulla using quantitative receptor autoradiography

Peptides. 2006 Jun;27(6):1532-7. doi: 10.1016/j.peptides.2005.10.004. Epub 2005 Nov 14.

Abstract

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.

MeSH terms

  • Animals
  • Autoradiography
  • Binding Sites
  • Binding, Competitive
  • Humans
  • Kidney Medulla / metabolism*
  • Kinetics
  • Ligands
  • Protein Binding
  • Rats
  • Rats, Inbred SHR
  • Rats, Inbred WKY
  • Rats, Sprague-Dawley
  • Receptors, G-Protein-Coupled / metabolism
  • Species Specificity
  • Urotensins / chemistry*
  • Urotensins / metabolism

Substances

  • Ligands
  • Receptors, G-Protein-Coupled
  • Urotensins
  • Uts2r protein, rat
  • urotensin II