Characterization of endometrial and myometrial oxytocin receptors in the non-pregnant ewe

Abstract

ABSTRACT Oxytocin-binding sites in the endometrium and myometrium of the non-pregnant ewe were characterized. [3H]Oxytocin bound to a single site in both tissues with high affinity; dissociation constants were determined to be 1·96 nmol/l in endometrium and 2·12 nmol/l in myometrium. Oxytocin binding was enhanced by divalent cations with a similar order of potency in both tissues: Co2+> Mn2+> Ni2+> Mg2+ > Zn2+> Ca2+. The endometrial and myometrial binding sites showed the same specificity for oxytocin analogues and related peptides, having high affinity for oxytocin, [Arg8]-vasopressin, [Lys8]-vasopressin, and the oxytocin-specific agonists [Gly7]-oxytocin and [Thr4,Gly7]-oxytocin. The results suggest that oxytocin receptors present in the endometrium and myometrium of the ewe are similar both to each other and to classical oxytocin receptors. Journal of Endocrinology (1989) 123, 11–18