A reversible radioligand specific for the ETB receptor: [125I]Tyr13-Suc-[Glu9,Ala11,15]-endothelin-1(8- 21), [125I]IRL 1620

Biochem Biophys Res Commun. 1992 Jun 30;185(3):867-73. doi: 10.1016/0006-291x(92)91707-w.


Suc-[Glu9,Ala11,15]-endothelin(ET)-1(8-21), IRL 1620, is a linear ET-analog specific for the ET-isopeptide-nonselective ETB receptor. The radio-iodinated analog, [125I]IRL 1620, showed a single class of saturable binding to the ETB receptors in porcine lung membranes with a Kd of 18 pM and a Bmax of 930 fmol/mg protein, which are almost comparable to the values obtained with [125I]ET-3 (6 pM and 900 fmol/mg protein). In competitive binding assays with [125I]IRL 1620, unlabeled ET-1, ET-3, IRL 1620 and [monoiodo-Tyr13]-IRL 1620 showed almost identical displacement curves with Ki of 8 to 16 pM. However, [125I]IRL 1620 was dissociated from the binding sites by addition of an excess amount (100 nM) of any of these unlabeled peptides, each with the same t1/2 of 100 min. This was in marked contrast to [125I]ET-3 which was hardly dissociated from the binding sites.

MeSH terms

  • Animals
  • Binding, Competitive
  • Cell Membrane / metabolism
  • Endothelins / metabolism*
  • Iodine Radioisotopes
  • Kinetics
  • Lung / metabolism*
  • Peptide Fragments / metabolism*
  • Radioligand Assay
  • Receptors, Cell Surface / metabolism*
  • Receptors, Endothelin
  • Swine


  • Endothelins
  • Iodine Radioisotopes
  • Peptide Fragments
  • Receptors, Cell Surface
  • Receptors, Endothelin
  • sovateltide