title: Receptor binding and biologic activity of synthetic ET-1 peptides in the retinal pericyte.
abstract: OBJECTIVE
  The purpose of this study was to examine the effect of synthetic endothelin (ET)-1 peptides with antigenic potential for binding and biologic activity using an in vitro model of microvascular pericytes.
  
  
  METHODS
  All possible sequential hexapeptide fragments of endothelins -1, -2, and -3 were synthesized on polyethylene rods and tested for reactivity with antibodies for ET-1 and ET-3. The most highly antigenic peptide ET-1[3-8] and the least antigenic ET-1[1-6], which gave low reactivity in the enzyme-linked immunosorbent assay (ELISA), were synthesized. The C-terminal hexapeptide ET-1[16-21], which has been reported as an ETB receptor agonist but which gave no reactivity in the ELISA, also was investigated. The synthesized ET analogues were tested for receptor binding, inositol phosphate generation, and mitogenesis in bovine retinal pericytes.
  
  
  RESULTS
  ET-1[16-21] partially inhibited both [125I]-ET-3 binding at high concentrations, as did ET-1[1-6]. In contrast, ET-1[3-8] displaced labeled ET-1 binding but not labeled ET-3 binding. None of the peptides had any significant mitogenic or second-messenger responses when compared to those elicited by the full ET-1 molecule.
  
  
  CONCLUSIONS
  The result of the current work shows that the sequence, ET[3-8], is involved in isopeptide-specific binding to ETA receptors, but it suggests that other regions of the molecule are necessary for full bioactivity in microvascular pericytes.
authors.affiliation: Department of Opthalmology, Queen's University of Belfast, Northern Ireland.
authors.forename: D M
authors.initials: DM
authors.lastname: McDonald
authors.forename: J R
authors.initials: JR
authors.lastname: Bailie
authors.forename: D B
authors.initials: DB
authors.lastname: Archer
authors.forename: U
authors.initials: U
authors.lastname: Chakravarthy
mesh_terms: D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D002417:Cattle; D002478:Cells, Cultured; D016232:Endothelins / Q000138:chemical synthesis / Q000276:immunology / Q000378:metabolism* / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D016056:Immunodominant Epitopes / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology; D007295:Inositol Phosphates / Q000378:metabolism; D008934:Mitogens; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000276:immunology / Q000378:metabolism* / Q000494:pharmacology; D017466:Receptors, Endothelin / Q000378:metabolism*; D012171:Retinal Vessels / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
chemical_list: D016232:Endothelins; D016056:Immunodominant Epitopes; D007295:Inositol Phosphates; D008934:Mitogens; D010446:Peptide Fragments; D017466:Receptors, Endothelin