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Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Oxytocin receptors were measured in myometrium and intercaruncular endometrium of cows during pregnancy and parturition. Concentrations of estradiol-17 beta, estrone, and progesterone in peripheral blood were also measured. Receptor concentrations in the endometrium rose almost 200-fold from Day 20 to term (p < 0.0001, ANOVA), from 40 +/- 11 to 7300 +/- 1430 fmol/mg protein. Myometrial receptor concentrations increased 10-fold from 180 +/- 36 fmol/mg on Day 20 to 1850 +/- 360 fmol/mg protein at term (p < 0.0001, ANOVA). During labor, endometrial receptors (6600 +/- 1300 fmol/mg) remained at prelabor values, whereas myometrial receptor concentrations had decreased to 1190 +/- 316 fmol/mg (not significant) and declined further postpartum. Plasma concentrations of progesterone declined from 4-5 ng/ml to about 2 ng/ml between Days 250 and 282 and dropped to < 0.2 ng/ml shortly before delivery. Plasma concentrations of estrone and estradiol-17 beta were below 10-20 pg/ml until Day 230. Estrone concentrations were significantly (p < 0.05) increased by Day 250 and estradiol-17 beta by Day 270, and then both rose rapidly. During labor, plasma estrone was 1135 +/- 245 pg/ml and plasma estradiol-17 beta was 226 +/- 131 pg/ml. The molar ratio of estrone and estradiol-17 beta to progesterone rose from less than 0.01 to 4.4 during labor, and was correlated with oxytocin receptor concentrations in endometrium (r = 0.5160, p < 0.001), but not those in myometrium (r = 0.0122). The regulation of oxytocin receptors by ovarian hormones in the two tissues may therefore differ.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Oxytocin and bovine parturition: a steep rise in endometrial oxytocin receptors precedes onset of labor. 133 77

Intact cyclic ewes have been used in experiments designed to examine the mechanism by which uterine oxytocin receptor synthesis is controlled during the oestrous cyclic. Previous experiments have shown that the prostaglandin F2 alpha analogue cloprostenol is luteolytic in ewes receiving oxytocin by continuous intra-venous infusion. When ewes receiving oxytocin are given cloprostenol uterine oxytocin receptor concentrations are raised, whereas in animals receiving oxytocin alone, they remain low. To investigate whether inhibition of oxytocin receptor binding activity by oxytocin is either dependent on elevated plasma progesterone concentrations or over-ridden by oestrogens secreted by ovarian follicles maturing as a result of cloprostenol treatment, ewes were given oxytocin by continuous intravenous infusion (3 nmol h-1) between Days 12 and 17 after oestrus and one of the following: no further treatment; cloprostenol [125 micrograms intramuscularly (i.m.)] on Day 15; progesterone, by subcutaneous implant, from Day 14 with cloprostenol on Day 15; medroxyprogesterone acetate (MPA; 6 mg depot i.m.) on Day 14 followed by cloprostenol on Day 15; or oestradiol-17 beta (2.75 mumol i.m.) on Days 14 and 15. Concentrations of oxytocin receptor were measured at autopsy on Day 17 in caruncular endometrium, intercaruncular endometrium and myometrium. Ovarian follicles and corpora lutea were examined to determine the effect of treatment on these tissues. Treatment with oxytocin alone resulted in the maintenance of corpora lutea, reduced follicular development and a low concentration of uterine oxytocin receptor. Cloprostenol initiated luteolysis in oxytocin-treated ewes. This was associated with a high level of oxytocin receptor binding activity in all ewes except those receiving exogenous progesterone.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of continuous infusion of oxytocin on ovarian function and uterine oxytocin receptor concentration in the cyclic ewe. 133 7

The endometrial oxytocin receptor occupies a central point in the choice between luteolysis and pregnancy in ruminants. Receptor expression determines the time at which luteolysis occurs in nonpregnant animals, and thereby determines the duration of the oestrous cycle. Inhibition of receptor expression by trophoblast interferon (IFN) blocks the process of luteal regression and leads to continued progesterone secretion and the successful growth of the conceptus. Trophoblast IFN is probably required from the time of normal luteolysis during the cycle until luteal oxytocin concentrations of pregnancy decline, thus removing the stimulatory mechanism for the release of the episodes of prostaglandin F2 alpha required for luteolysis.
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PMID:Role of the oxytocin receptor in the choice between cyclicity and gestation in ruminants. 133 56

A type I interferon (IFN) secreted by the trophoblast of early sheep and cow embryos is thought to be responsible for the maternal recognition of pregnancy. The expression of trophoblast IFN is tissue specific and temporally controlled. However, the isolated bovine trophoblast IFN promoter did not confer tissue specificity on the expression of a bacterial chloramphenicol acetyl transferase (CAT) reporter gene, and could not be induced by virus, unlike other type I IFNs. Trophoblast IFN acts locally within the uterus to prevent luteolysis and prolong progesterone secretion. Endometrial IFN receptors are present, and trophoblast IFN decreases expression of endometrial oxytocin receptor and increases expression of endometrial beta 2-microglobulin, MHC class I antigens and Mx (a mediator of IFN antiviral activity) only in the pregnant horn of pregnant ewes with a transected uterus. The primary effect of trophoblast IFN during early pregnancy appears to be an inhibition of oxytocin receptor expression, although studies in ovariectomized ewes suggest that luteal oxytocin may be required to facilitate the inhibition of prostaglandin F secretion by trophoblast IFN. An investigation of the isolated oxytocin receptor promoter should confirm its critical role in the maternal recognition of pregnancy.
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PMID:Trophoblast interferons in early pregnancy of domestic ruminants. 133 57

Oxytocin infusions were initiated on day 10 of the oestrous cycle in ewes, and luteal regression was induced by injection of 100 micrograms cloprostenol on day 12. Blood samples were collected at frequent intervals via an indwelling jugular vein cannula to measure concentrations of progesterone and luteinizing hormone (LH) during the luteal and follicular phases in saline (n = 6) and oxytocin (n = 5) infused animals. The oxytocin infusion maintained peripheral plasma concentrations of 53 +/- 3.2 pg oxytocin ml-1 (mean +/- SEM) compared with values of about 1 pg ml-1 during oestrus in control ewes. Oxytocin infusion had no effect on luteal phase progesterone concentrations, the timing of luteolysis, basal luteinizing hormone (LH) secretion, LH pulse frequency, or the timing or height of the LH surge. Treated ewes came into oestrus significantly earlier than controls (P < 0.05) but ovulated normally. Uterine samples collected 96 h after cloprostenol injection (approximately day 2 of the cycle) showed that oxytocin receptor concentrations were significantly higher in the endometrium in ewes that had been given a 5 day oxytocin infusion than in control animals (556 and 262 fmol mg-1 protein, respectively: geometric means from ANOVA, P < 0.001), whereas myometrial receptor concentrations were not affected (113 and 162 fmol mg-1 protein, respectively). We conclude that the previously reported delay in luteal development caused by oxytocin infusion (Wathes et al., 1991) is not due to the inhibition or delay of ovulation, but must instead occur via a direct influence on the developing corpus luteum.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of oxytocin infusion on secretion of progesterone and luteinizing hormone and the concentration of uterine oxytocin receptors during the periovulatory period in cloprostenol-treated ewes. 133 45

The concentrations of oxytocin receptors were measured in intercaruncular and caruncular endometrium, fetal cotyledons, chorioallantois and amnion during pregnancy and parturition in cows. Tissues were obtained on days 20 (endometrium only), 50, 100, 150, 200, 225, 250, 275, at term (days 280-284), during labour and within 24 h after calving. Receptor concentrations in intercaruncular endometrium were low on day 20 of pregnancy, 39 +/- 11 fmol mg-1 protein. By day 50, receptor concentrations had increased more than tenfold to 572 +/- 52 fmol and rose steadily until day 250 and then levelled off at about 4500 fmol mg-1. Shortly before parturition, on day 282 +/- 1, a further rise to 7300 +/- 1418 fmol mg-1 was observed, these concentrations were maintained throughout labour. By contrast, caruncular endometrial receptor concentrations remained low until term, mean 145 +/- 15 fmol mg-1, and then rose to 720 +/- 163 fmol mg-1 during labour (cervix 17 cm--fully dilated). Fetal cotyledons and membranes had very low oxytocin receptor concentrations during most of pregnancy, on average only 20 fmol mg-1 protein. At term and during labour, receptor concentrations were significantly increased in both tissues. Mean concentrations during labour were 163 +/- 36 fmol mg-1 for cotyledons, 270 +/- 61 fmol mg-1 for chorioallantois and 311 +/- 121 fmol mg-1 for amnion.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Concentration of oxytocin receptors in the placenta and fetal membranes of cows during pregnancy and labour. 133 57

Studies were performed to identify the receptor that mediates AVP-stimulated phosphoinositide (PI) hydrolysis in cultured rat inner medullary collecting tubule (RIMCT) cells. While the selective V1 receptor agonist [Ho1, Phe2, Orn8] VT has no effect on inositol trisphosphate (IP3) production over the range of 10(-13)-10(-7) M, the selective V2 receptor agonist VDAVP stimulates IP3 production in dose-dependent fashion. Oxytocin stimulates IP3 production in dose-dependent fashion as well. AVP-stimulated phospholipase C activity is not inhibited by the V1 receptor antagonist d(CH2)5Tyr(Me)AVP(10(-7) M) but is eliminated by the V2 receptor antagonist d(CH2)5DTyr(Et)VAVP (10(-7) M). Similarly, the response to oxytocin is eliminated by the V2 receptor antagonist. The selective oxytocin receptor agonist [Thr4, Gly7] oxytocin does not stimulate cAMP production in RIMCT cells but does promote PI hydrolysis. The selective oxytocin receptor antagonist desGlyNH2d(CH2)5[Tyr(Me)-Thr4]OVT (10(-7) M) does not inhibit AVP-stimulated cAMP production but eliminates IP3 production in response to AVP or the V2 receptor agonist VDAVP. These studies demonstrate that AVP or a V2 receptor agonist stimulate PI hydrolysis in cultured RIMCT cells via occupancy of the oxytocin receptor.
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PMID:Vasopressin-stimulated phosphoinositide hydrolysis in cultured rat inner medullary collecting duct cells is mediated by the oxytocin receptor. 164 53

Oxytocin, when administered centrally, has been associated with the modulation of various social initiatives including maternal and sexual behaviors. The nature of these effects depends on gonadal hormone status. In the present experiments, we investigated the effects of centrally administered oxytocin on the behavior of pair-housed male squirrel monkeys during interactions with a familiar female monkey. Pairs of male squirrel monkeys established reliable and persistent dominance relationships with dominant males showing increased sexual and aggressive behavior as well as higher plasma concentrations of testosterone. Oxytocin (0.1, 1.0 micrograms) increased the sexual and aggressive behavior of dominant monkeys without affecting these measures in the subordinate monkeys. In contrast to these effects in the dominant monkeys, oxytocin increased associative and marking behaviors only in subordinate monkeys. Central administration of the oxytocin receptor antagonis d(CH2)5 [Tyr(Me)2, Thr4,Tyr-NH2(9)] OVT (OTA; 0.05 microgram) had no intrinsic effect on behavior but blocked the effects of exogenous oxytocin. To investigate further the specificity of oxytocin's effects on social behavior, we administered the structurally related peptide arginine vasopressin under identical conditions. Vasopressin (0.5, 5.0 micrograms) decreased social behaviors and increased motor activity in both dominant and subordinate monkeys. Previous studies in rodents have demonstrated that oxytocin receptors are induced by gonadal steroids in a regionally specific fashion. The status-related behavioral effects of oxytocin in the squirrel monkey may reflect differences in brain oxytocin receptor density associated with the higher concentrations of testosterone in the dominant animal. Alternatively, the status-related effects may depend on the conditioned behavioral differences associated with social organization.
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PMID:Social status in pairs of male squirrel monkeys determines the behavioral response to central oxytocin administration. 164 3

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) and day +3 of the oestrous period). Oxytocin receptors were localized autoradiographically in sections of uterine tissue, using the 125I-labelled oxytocin receptor antagonist [1-(beta-mercapto-beta, beta-cyclopentamethylene propionic acid), 2-(ortho-methyl)-Tyr2,Thr4,Orn8, Tyr9-NH2]-vasotocin (125I-labelled OTA). There was some variation in the pattern of 125I-labelled OTA labeling between different uterine tissue samples from the same ewe and also between samples obtained from different ewes thought to be at the same stage of the oestrous cycle. A clear overall pattern did, however, emerge with 125I-labelled OTA-binding sites distributed between luminal epithelial cells, glandular epithelial cells and caruncular stromal cells to varying extents on different days of the cycle. During the luteal phase (days 5-12) clear specific labelling of endometrial tissue was generally absent. On day 14 labelling was evident on the luminal epithelium, but only in nine tissue samples out of a total of 18 studied, indicating that the entire luminal surface did not contain oxytocin receptors at this time. Between the day before oestrus and day 3 of the oestrous cycle the luminal epithelium was consistently labelled.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Autoradiographic localization of oxytocin receptors in the endometrium during the oestrous cycle of the ewe. 165 40

Several recent studies have suggested that the neurohypophyseal peptide oxytocin may have a role within the brain to mediate various forms of affiliative behavior. As the regulation of oxytocin function may be largely determined by the number and distribution of its membrane bound receptor, we investigated oxytocin receptor distribution in two Peromyscus species selected for differences in affiliative behavior. Using in vitro receptor autoradiography with the selective oxytocin receptor ligand [125I]d(CH2)5[Tyr(Me)2,Tyr-NH9(2)]OVT ([125I]OTA), we compared Peromyscus maniculatus, a polygamous species, to Peromyscus californicus, a monogamous species. Marked species differences in the distribution of [125I]OTA were apparent in several brain areas, including olfactory pathways, bed nucleus of the stria terminalis, amygdala, dorsal lateral septum, and several cortical regions. In addition, gender differences in the binding pattern were evident in several regions, mostly due to sexually dimorphic patterns in the polygamous species, P. maniculatus. To further compare these species, the binding of a [3H]arginine-vasopressin antagonist was assessed in alternate sections from those used for [125I]OTA. Relative to oxytocin receptors, binding to arginine-vasopressin receptors showed fewer species differences, although the monogamous species appeared to have more arginine-vasopressin receptors in the neocortex and lateral septum. The striking differences in oxytocin receptor distribution are consistent with earlier studies in other rodents, suggesting that oxytocin may have an important role for mediating species-typical patterns of social affiliation.
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PMID:The comparative distribution of forebrain receptors for neurohypophyseal peptides in monogamous and polygamous mice. 165 22


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