Vasopressin (V1) receptor characteristics in rat aortic smooth muscle cells

V. Gopalakrishnan, Y. Xu, P. V. Sulakhe, Christopher Triggle, J. R. McNeill

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Abstract

We report saturable, high-affinity, specific, reversible binding sites for both [3H]arginine vasopressin ([3H]AVP) and d(CH2)5Tyr(Me)-[3H]AVP, a V1-selective antagonist, in cultured smooth muscle cells obtained from rat aorta (RA) and rat mesenteric artery (RMA). Specific binding of [3H]AVP had the following characteristics in adherent monolayers of RA and RMA smooth muscle cells: dissociation constant (K(D)) = 1.42 and 1.23 nM and maximal binding capacity (B(max)) = 9,500 and 29,910 sites/cell, respectively. Lower K(D) and higher B(max) values were detected for 3H-labeled V1 antagonist binding to both types of cells. Complete dissociation of [3H]AVP binding to RA cells occurred in a biphasic manner with two rate constants of dissociation, suggesting high- and low-affinity states of the binding site for the agonist interaction. Partial dissociation of the antagonist-specific binding occurred, and it was monophasic, suggesting interaction of the 3H-labeled V1 antagonist radioligand to the high-affinity binding state. Inhibition constant (K(i)) values determined by competitive inhibition of [3H]AVP binding to RA cells by a series of AVP-related peptide analogues and antagonists were consistent with the saturation data. AVP in a concentration-dependent manner induced the accumulation of inositol phosphates [mean effective concentration (EC50) 1 nM] in the adherent RA cells. The free cytosolic Ca2+ level in the dispersed RA smooth muscle cells was increased by AVP (EC50 8.1 nM). Pretreatment with the V1 antagonist abolished these AVP-evoked responses. The data support the conclusion that the agonist binding occurs at a homogeneous population of V1-subtype receptors in the high-affinity (K(D)) = ~1 nM) state and that these receptors are functionally coupled to phospholipase C.

Original languageEnglish
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume261
Issue number6 30-6
Publication statusPublished - 1991
Externally publishedYes

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Keywords

  • Angiotensin II
  • Endothelin-1
  • Fura-2 fluorescence
  • Inositol phosphates
  • Intracellular calcium ion concentration
  • Vascular smooth muscle cells
  • Vasopressin analogues and antagonists

ASJC Scopus subject areas

  • Physiology
  • Medicine(all)

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