AJP - Endocrinology and Metabolism, Vol 254, Issue 1 E31-E38, Copyright © 1988 by American Physiological Society

ARTICLES

[3H]-[Thr4,Gly7]OT: a highly selective ligand for central and peripheral OT receptors

J. Elands, C. Barberis and S. Jard
Centre National de la Recherche Scientifique-Institut National de la Sante et de la Recherche Medicale de Pharmacologie-Endocrinologie, Montpellier, France.

Oxytocin receptors in rat hippocampal synaptic plasma membranes were compared with mammary gland and uterine oxytocin receptors. For this purpose, a highly specific oxytocic agonist [Thr4,Gly7]oxytocin was tritiated. We demonstrated that this ligand labels oxytocin receptors selectively. Scatchard analyses revealed a high affinity for all the oxytocin receptors investigated, with equilibrium dissociation constants between 1.0 and 2.0 nM. Binding appeared to take place at a single population of receptor sites. Competition experiments confirmed the high affinity of arginine vasopressin for hippocampal oxytocin receptors but also revealed that mammary gland and uterine oxytocin receptors do not discriminate more efficiently between oxytocin and arginine vasopressin. This lack in specificity is not affected by applying different concentrations of Mg ions.

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