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Oxytocin (OT) has long been used as an uterotonic during labor management in women, and yet responses to OT infusion remain variable and unpredictable among patients. The investigation of oxytocin receptor (OTR) regulation will benefit labor management, because the clinical practice of continuous iv infusion of OT is not optimal. As with other G(More)
Anoestrous Romney Marsh ewes with (+P) and without (-P) progesterone pretreatment were induced to ovulate by multiple low-dose injection of GnRH followed by a bolus injection of GnRH. Luteal function was assessed by twice daily measurement of plasma progesterone. Animals were slaughtered on Days 3 or 5 after the end of GnRH treatment and CL and endometrium(More)
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(More)
Oxytocin and the related peptide [Arg8]vasopressin (AVP) have previously been shown to bind with equally high affinity to oxytocin binding-sites (presumed oxytocin receptors) present within the uterus and oviduct of oestrous ewes. There is a possibility, therefore, that AVP mediates oxytocic actions through these binding sites. For the present study, ewes(More)
This study has localised oxytocin receptor (OTR) mRNA expression within the cervix of non-pregnant ewes and related this to changes in the sensitivity of the cervical musculature to administered oxytocin (OT) during the oestrous cycle by recording electromyographic (EMG) activity. Cervices were collected from 34 ewes at specified time points throughout the(More)
Some of the binding characteristics of a novel oxytocin receptor ligand 125I-labelled [1-(beta-mercapto-beta, beta-cyclopentamethylene propionic acid), 2-(ortho-methyl)-Tyr2,Thr4,Orn8,Tyr9-NH2]-vasotocin ([125I]OTA) have been determined in the sheep uterus. The compound was subsequently used for the autoradiographic localization of oxytocin receptors in the(More)
The presence of oxytocin receptors in ovine oviduct has been investigated. High-affinity binding sites for [3H]oxytocin were detected in crude membrane fractions prepared from the oviducts of ewes killed during the oestrous period. The dissociation constant calculated for these sites in competition studies was 1.7 nmol/l. Similar dissociation constants were(More)
The present study was designed to determine the localization of the endometrial oxytocin receptor during the ovine oestrous cycle, particularly on day 14, the time of initiation of luteal regression in the ewe. Samples were obtained from 29 ewes at different stages of the oestrous cycle (several during the luteal phase and on every day between day 14 (-2)(More)