Do α2-adrenoceptors and imidazoline binding sites coexist in the human term placenta? Evidence from direct binding studies

K. Bagaméry, L. Kovács, T. Nyári, G. Falkay

Research output: Contribution to journalArticle

4 Citations (Scopus)


α2-Adrenergic receptors and non-adrenergic imidazoline binding sites (IBS) in human placental membranes were investigated by means of the radioligands [3H]-RX 821002 and [3H]-RX 781094 (idazoxan) respectively. Human term placentae (38-40 weeks) were obtained immediately after vaginal delivery. The specific binding of the α2-subtype-selective [3H]-RX 821002 confirms the presence of α2-adrenoceptors in the human placenta, while [3H]-idazoxan binds to non-adrenergic IBS. The sites were characterized by displacement analyses with various imidazoline and non-imidazoline drugs. The presence of an endogenous ligand for IBS has not yet been demonstrated. Clonidine displacing substance (CDS) was recently identified as agmatine; it recognizes both α2 and imidazoline receptors. This phenomenon was studied in crude placental membranes. The studies revealed that: (i) α2-adrenoceptors coexist with non-adrenergic IBS in human placental membranes; (ii) there is a strong probability that α2-adrenoceptors and IBS are pharmacologically distinct; and (iii) agmatine binds to placental α2 and imidazoline receptors with different affinities.

Original languageEnglish
Pages (from-to)387-391
Number of pages5
JournalMolecular Human Reproduction
Issue number4
Publication statusPublished - Apr 1 1998


  • Agmatine
  • Imidazoline binding site
  • Term placenta
  • α-adrenoceptor

ASJC Scopus subject areas

  • Reproductive Medicine
  • Embryology
  • Molecular Biology
  • Genetics
  • Obstetrics and Gynaecology
  • Developmental Biology
  • Cell Biology

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