Multiple [<sup>3</sup>H]-Oxytocin Binding Sites in Rat Myometrial Plasma Membranes

Crankshaw, Denis; Gaspar, V.; Pliška, V.

doi:10.3109/10799899009064670

Cited by 26 publications

(15 citation statements)

References 32 publications

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“…The present study revealed a single population of high-affinity binding sites using [' HJoxytocin concen¬ trations of up to 20 nmol/1; however, in addition to a high-affinity site, two additional lower affinity oxytocinbinding sites have been demonstrated in cultured sheep myometrial cells (Pliska et al 1986) and rat myometrial plasma membranes (Crankshaw et al 1990), which would not have been detected here. It has been argued that these lower affinity sites are of physiological significance to the actions of oxytocin (Crankshaw et al 1990, Pliska 1991.…”

Section: Discussioncontrasting

confidence: 52%

Characterization and localization of a putative oxytocin receptor in the cervix of the oestrous ewe

Matthews

Ayad²

1994

Journal of Endocrinology

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The purpose of the present study was to investigate the presence of high-affinity oxytocin-binding sites (putative oxytocin receptors) in the cervix of the non-pregnant ewe. [3H]Oxytocin binding to the peripheral layers of cervical tissue (comprising the serosal layer and the least dense collagenous and muscular layers) and the remaining dense collagenous cervical tissue were studied separately. [3H]Oxytocin-binding sites were detected in membrane fractions prepared from both of these regions, but binding to the peripheral cervix was variable and binding site concentrations were low, hence these were not characterized further. A high-affinity oxytocin-binding site, having a dissociation constant of 1.8 nmol/l, was characterized in the dense collagenous regions of the cervix of ewes killed during the oestrous period. Similar dissociation constants were determined for [Arg8]-vasopressin and the oxytocin-specific agonist [Thr4, Gly7]-oxytocin in competition studies. [3H]Oxytocin binding to peripheral cervical tissue and to the dense collagenous cervix was generally low or undetectable during the luteal phase, but increased in both tissues around the time of luteolysis. Although specific binding to both tissues was variable during the oestrous period, it was higher at this time than during the luteal phase. [3H]Oxytocin-binding site concentrations were also found to be higher within the inner dense collagenous cervix of oestrous ewes than of pregnant, ovariectomized or anoestrous animals.(ABSTRACT TRUNCATED AT 250 WORDS)

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Section: Discussioncontrasting

confidence: 52%

Characterization and localization of a putative oxytocin receptor in the cervix of the oestrous ewe

Matthews

Ayad²

1994

Journal of Endocrinology

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“…Only one class of binding sites was detected (K d ϭ 6.3 ϫ 10 Ϫ9 M), which is in keeping with results obtained in saturation and homologous competition studies in pregnant women [11,14] but contrasts with similar studies in rats, sheep and cattle [19,20]. In these studies at least two saturable binding sites were found (approx.…”

Section: Discussionsupporting

confidence: 80%

“…In these studies at least two saturable binding sites were found (approx. K d ϭ 5 ϫ 10 Ϫ9 M and 4 ϫ 10 Ϫ7 M) [19,20]. This raised the question of the identity of the oxytocin receptor [19].…”

Section: Discussionmentioning

confidence: 99%

“…This range did not permit the investigators to determine whether binding sites with K d s Ͼ 10 Ϫ8 M exist. In experiments that measured binding over an extended range of oxytocin concentrations (10 Ϫ10 to 10 Ϫ5 M) in myometrium and endometrium of sheep, rats, and cattle, binding sites with K d s of approximately 5 ϫ 10 Ϫ9 M, 4 ϫ 10 Ϫ7 M (both saturable), and Ͼ 10 Ϫ5 M (possibly not fully saturable) were identified [19,20]. In pregnant women near term, oxytocin saturation studies and homologous competition experiments over a similar range of oxytocin concentrations (10 Ϫ11 to 10 Ϫ5 M) suggested that only one class of binding sites exists (K d ϭ 6 ϫ 10 Ϫ10 M), while self-and cross-displacement studies indicated the existence of 2 binding sites for oxytocin with K d s of 4.5 ϫ 10 Ϫ10 M and 8.4 ϫ 10 Ϫ10 M [11].…”

Section: Introductionmentioning

confidence: 99%

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Oxytocin Receptors in Guinea Pig Myometrium Near Term and During Labor1

Schellenberg

Pliška

Lutz

2000

Biology of Reproduction

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Oxytocin receptors in myometrium of women, rats, and rabbits rise markedly before the onset of labor, suggesting a role in the initiation of labor. In guinea pigs, a previous study reported no such rise by one-point determination of oxytocin binding. The purpose of this study was to use a more rigorous method to determine whether the binding characteristics of myometrial oxytocin receptors change in relation to labor in guinea pigs. Competitive binding studies were carried out in microsomes from inner and outer myometrium between 42 days of gestation and labor. Binding to analogs was also tested. Data were analyzed with affinity spectra and LIGAND. Oxytocin bound to one site with a dissociation constant of 6.3 +/- 0.65 x 10(-9) M. Binding capacity was 1.0 +/- 0.1 x 10(-12) mol/mg protein. The Hill coefficient was near unity. No significant changes occurred with gestation or labor in dissociation constant, binding capacity, or Hill coefficient (all P >/= 0.2, nested ANOVA). Binding capacity was higher in the outer than in the inner layer (1.2 +/- 0.2 vs. 0.8 +/- 0.1 x 10(-12) mol/mg protein, P = 0.02), but the dissociation constants were similar. Differences existed in the dissociation constants of the analogs tested. The main conclusion is that oxytocin receptors are unlikely to have a regulatory role in the initiation of labor in guinea pigs.

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“…Few data are available as regards OT receptor subtypes and mainly concern the uterus. Thus, three OT receptor subtypes according to their affinity for OT have been reported on myometrial plasma membranes in the rat (Crankshaw et al 1990). In the same species, the effects of OT on the myometrium and the endometrium are mediated by two OT receptor subtypes having distinct pharmacological characteristics (Chan et al 1993).…”

Section: Discussionmentioning

confidence: 99%

Two oxytocin-binding site subtypes in rat kidney: pharmacological characterization, ontogeny and localization by in vitro and in vivo autoradiography

Arpin-Bott¹,

Waltisperger²,

Freund-Mercier³

et al. 1997

Journal of Endocrinology

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The localization of oxytocin (OT)-binding sites in the developing rat kidney and their pharmacological characterization were investigated by means of autoradiographic techniques. The cellular localization was studied by application of the histoautoradiographic technique to (1) frozen sections and semithin sections from kidney slices incubated in vitro in the presence of a 125I-labelled OT antagonist and (2) frozen and semithin sections from kidneys after in vivo systemic infusion of the radioligand. Pharmacological characteristics were determined in competition experiments by using quantitative film autoradiography. Specific OT-binding sites were first detected at embryonic day 17 (E17) in the cortex. At early stages up to postnatal days (PN30), the cortical OT-binding sites were highly concentrated on the juxta- and paraglomerular portion of the distal tubule; in the adult they were restricted to the macula densa. In the medulla, OT-binding sites were first detected at E19 when this region is forming; they were localized on the thin limb of Henle's loop. These data obtained by in vivo binding were confirmed by in vivo binding at PN30 which showed, in addition, the presence in one rat of OT-binding sites in the inner stripe of the outer medulla. At all stages examined (PN15 to PN90), cortical OT-binding sites had a higher selectivity for OT versus vasopressin (IC50 = 0.78 +/- 0.04 nM and 8 +/- 0.5 nM respectively at PN90) than medullary sites (IC50 = 1.9 +/- 0.27 nM and 2 +/- 1.13 nM respectively at PN90). These data suggest that the OT-binding sites of the macula densa and thin Henle's loop, detected in the rat kidney, represent two subtypes of OT receptors which could mediate distinct effects of OT on kidney function.

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Multiple [³H]-Oxytocin Binding Sites in Rat Myometrial Plasma Membranes

Cited by 26 publications

References 32 publications

Characterization and localization of a putative oxytocin receptor in the cervix of the oestrous ewe

Characterization and localization of a putative oxytocin receptor in the cervix of the oestrous ewe

Oxytocin Receptors in Guinea Pig Myometrium Near Term and During Labor1

Two oxytocin-binding site subtypes in rat kidney: pharmacological characterization, ontogeny and localization by in vitro and in vivo autoradiography

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Multiple [3H]-Oxytocin Binding Sites in Rat Myometrial Plasma Membranes

Cited by 26 publications

References 32 publications

Characterization and localization of a putative oxytocin receptor in the cervix of the oestrous ewe

Characterization and localization of a putative oxytocin receptor in the cervix of the oestrous ewe

Oxytocin Receptors in Guinea Pig Myometrium Near Term and During Labor1

Two oxytocin-binding site subtypes in rat kidney: pharmacological characterization, ontogeny and localization by in vitro and in vivo autoradiography

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Multiple [³H]-Oxytocin Binding Sites in Rat Myometrial Plasma Membranes