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

An experiment was conducted to (i) determine whether administration of recombinant bovine interferon-alpha I1 (rBoIFN-alpha) attenuates oxytocin-induced release of prostaglandin F-2 alpha and (ii) confirm previous observations that rBoIFN-alpha causes acute changes in body temperature and circulating concentrations of progesterone. Cows were treated twice a day from Day 14 to Day 17 after oestrus with a control regimen (bovine serum albumin (BSA), i.m. + BSA intrauterine (i.u.)), rBoIFN-alpha, i.u. + BSA, i.m. (rBoIFN-IU) or rBoIFN-alpha, i.m. + BSA, i.u. (rBoIFN-IM). On Day 17, plasma concentrations of 13,14-dihydro,15-keto-prostaglandin F-2 alpha (PGFM) were measured after injection of oxytocin. Cows treated with rBoIFN-IU and rBoIFN-IM had longer oestrous cycles and luteal lifespans than control cows. A hyperthermic response and decline in plasma concentrations of progesterone was noticed after administration of rBoIFN-alpha on Day 14. On other days, the hyperthermic response was not present and the decline in progesterone was less pronounced. There was no significant effect of rBoIFN-alpha on circulating concentrations of oestradiol between Days 14 and 17. The release of PGFM induced by oxytocin was lower in cows treated with rBoIFN-alpha than in control cows. Oxytocin caused increased plasma concentrations of PGFM in four of five control cows, two of five rBoIFN-IU cows and two of five rBoIFN-IM cows. The peak PGF-2 alpha response to oxytocin (peak value after injection minus mean concentration before injection) was 257.8 +/- 61.3 pg/ml for control cows, 100.7 +/- 40.8 pg/ml for rBoIFN-IU and 124.9 +/- 40.4 pg/ml for rBoIFN-IM. It is concluded that rBoIFN-alpha can reduce oxytocin-induced PGFM release and may therefore extend the lifespan of the corpus luteum by interfering with events leading to luteolytic release of PGF from the uterus. Administration of rBoIFN-alpha can cause acute changes in body temperature and circulating concentrations of progesterone that become less severe after repeated exposure to rBoIFN-alpha.
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PMID:Alteration of oestrous cycle length, ovarian function and oxytocin-induced release of prostaglandin F-2 alpha by intrauterine and intramuscular administration of recombinant bovine interferon-alpha to cows. 178 57

Spontaneous intraluminal pressure waves of diabetic nonpregnant uterus and contractile responses to oxytocin and prostaglandin F2 alpha (PGF 2 alpha) of both diabetic nonpregnant and diabetic pregnant uterus were investigated in vitro. Diabetes was induced by streptozotocin (STZ), 60 mg/kg for nonpregnant and 50 mg/kg for pregnant rats. Frequency of spontaneous intraluminal pressure waves of nonpregnant uterus was reduced in diabetic rats when compared with normal, but amplitude was slightly larger in diabetic than in normal uterus. Pressure-volume curves revealed that the compliance of nonpregnant diabetic uterus was remarkably reduced. Normal tubal side-circular muscle was significantly more sensitive to oxytocin and PGF 2 alpha than cervical one in contractile responses. This tendency was lost in diabetic nonpregnant uterus. Contractile responses of both tubal and cervical circular muscles to oxytocin were lower in nonpregnant diabetic than in normal rats, but those of longitudinal muscles were higher in diabetic nonpregnant than in normal rats. Cervical circular muscle of pregnant diabetic rats was more sensitive to both agents than those of normal. However, contractile responses of diabetic longitudinal muscle to both agents were higher than those of normal as in the case of nonpregnant uterus. The mechanism of diabetic changes of the nonpregnant and pregnant uterus was discussed.
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PMID:[Physiological studies on nonpregnant and pregnant uterus in experimentally diabetic rats]. 183 36

Maternal recognition of pregnancy in sheep, cattle and goats involves physiological mechanisms that result in protection of corpora lutea from luteolysis by modification or inhibition of uterine production of luteolytic pulses of prostaglandin (PG) F-2 alpha. Ovine, bovine and caprine luteal cells release oxytocin in a pulsatile manner during late dioestrus. Oxytocin then binds to its endometrial receptors and initiates luteolytic pulses of PGF-2 alpha. Ovine, bovine and caprine trophoblast protein-1 (oTP-1, bTP-1 and cTP-1) are secreted by the trophectoderm of conceptuses between Days 10 and 21-24 of pregnancy. These antiluteolytic proteins (oTP-1 and bTP-1) are primarily responsible for inhibiting uterine production of luteolytic amounts of PGF-2 alpha. During early pregnancy, the numbers of endometrial receptors for oxytocin are significantly lower in ewes and cows, and stimulatory effects of exogenous oxytocin on uterine production of PGF-2 alpha are correspondingly reduced or absent for ewes, cows and goats. Exogenous oestrogens can, through a uterine-dependent mechanism, stimulate synthesis of endometrial receptors for oxytocin and uterine production of PGF-2 alpha; an effect which is significantly attenuated during early pregnancy. These results suggest that oTP-1, bTP-1 and possibly cTP-1 exert their antiluteolytic effect(s) by: (1) inhibiting effects of oestrogen and/or progesterone necessary for synthesis of endometrial receptors for oxytocin; (2) inhibiting endometrial synthesis and/or recycling of oxytocin receptors directly; or (3) inducing the endometrium to synthesize an inhibitor of an enzyme(s) necessary for synthesis of PGF-2 alpha.
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PMID:Physiological mechanisms of pregnancy recognition in ruminants. 184 50

The role of PGF-2 alpha in determining the lifespan of corpora lutea in the post-partum beef cow was investigated. In control cows (N = 5) induced to ovulate at Day 28 to 36 post partum by injection of 1000 i.u. hCG, corpora lutea had an average lifespan of only 8 days. In cows pretreated with 6 mg implants of a progestagen (norgestomet, N = 4) for 9 days, with implant removal 2 days before injection of hCG, luteal lifespan averaged 17.5 days. Concentrations of PGF-2 alpha in 9 hourly samples of plasma collected from the posterior vena cava via indwelling catheters were higher on Days 4 through 9 after injection of hCG (P less than 0.05) in the cows with short-lived corpora lutea. Greater release of PGF-2 alpha could therefore be a major factor in premature luteal regression. Concentrations of PGFM and oxytocin did not differ between cows with corpora lutea of short or normal lifespan. In a second experiment, concentrations of PGF-2 alpha in plasma from the posterior vena cava were examined during treatment with norgestomet (N = 8) or in contemporary controls (N = 7). In progestagen-treated cows, PGF-2 alpha was higher than in control cows (P less than 0.05), beginning on Day 3 of treatment and peaking on Day 5. It is concluded that the post-partum uterus increases secretion of PGF-2 alpha very early after first exposure to endogenous or exogenous progestagen.
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PMID:Effects of progestagen treatment on concentrations of prostaglandins and oxytocin in plasma from the posterior vena cava of post-partum beef cows. 201 70

The secretion of prostaglandin (PG) F-2 alpha in response to intravenous injection of 100 i.u. oxytocin on Day 18 after oestrus was determined by measuring jugular venous concentrations of 13,14-dihydro-15-keto PGF-2 alpha (PGFM) in 7 pregnant, 6 cyclic and 2 inseminated non-pregnant heifers. Two other heifers received i.v. saline (controls). The immediate responses of pregnant heifers were smaller than in non-pregnant animals (P less than 0.05), as were baseline concentrations in the post-response period (P less than 0.05). Endometrial oxytocin receptor concentrations were higher in nonpregnant than pregnant heifers (P less than 0.05), but PGFM response to oxytocin challenge was not correlated with oxytocin receptor concentration. Oxytocin receptor concentrations on Day 18 were positively correlated with those of plasma oestradiol on Day 17 (P less than 0.01) and inversely with plasma progesterone concentrations on Day 18 (P less than 0.01). These findings confirm that PGF-2 alpha secretion in response to oxytocin challenge is attenuated in pregnant animals on the 18th day after oestrus and that, while the prevailing steroid environment is of importance in inducing oxytocin receptor activity, the secretion of PGF-2 alpha is not subsequently limited by oxytocin receptor numbers. The quantities of PGE-2, PGFM and PGF-2 alpha recovered in uterine flushings taken from heifers on Day 18 were greater in pregnant than other animals (P less than 0.01, P less than 0.05, P less than 0.001, respectively). Intrauterine concentrations of PGF-2 alpha and PGFM were not correlated with the plasma PGFM responses.
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PMID:Comparison of oxytocin/prostaglandin F-2 alpha interrelationships in cyclic and pregnant cows. 217 33

The relative contribution of systemic versus local (intrauterine) factors in the activation and stimulation of the sheep myometrium during labour was examined using an in-vivo myometrial explant preparation. Myometrial tissue alone (MYO) or with attached endometrium (ENDO/MYO) was removed from the pregnant uterine horn, sutured to a stainless-steel frame and placed into the omental fat. After 7-10 days the explants developed a pattern of electromyographic activity qualitatively similar to that of the uterine myometrium. Induction of preterm labour by infusion of ACTH (66.6 ng/min for 15 min every 2 h) to the fetus resulted in a reduction in plasma progesterone concentrations and increases in values of oestradiol-17 beta and 13,14-dihydro 15-keto PGF-2 alpha in maternal plasma. The onset of labour, which followed these endocrine changes, was characterized by an increase in EMG burst frequency and reduction in burst duration occurring simultaneously in both the uterine myometrium and in the explants. The response of the uterine and explant myometrium to oxytocin also exhibited a parallel significant increase over the 24-h period leading to delivery. No differences were apparent between the explants containing myometrial tissue alone or those comprising endometrial and myometrial tissue. There was no significant change in uterine or explant EMG activity, or oxytocin responsiveness, after saline administration to the fetus. The pattern of EMG activity changes during spontaneous labour were not distinguishable from those during ACTH-induced labour. As with oxytocin, the responsiveness of the explants to electrical stimulation increased significantly at labour compared to pre-labour. These data suggest that factors within the systemic circulation play a major role in both the onset of labour contractions and the increased response to electrical or hormonal (oxytocin) stimulation during parturition in sheep.
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PMID:Local and systemic control of myometrial contractile activity during labour in the sheep. 217 57

The effects of administration of progesterone and oestradiol on ovine endometrial oxytocin receptor concentrations and plasma concentrations of 13,14-dihydro-15-keto prostaglandin F-2 alpha (PGFM) after oxytocin treatment were determined in ovariectomized ewes. Ewes received progestagen pre-treatment, progesterone and/or oestradiol in 11 different treatment schedules. Progestagen pre-treatment decreased oxytocin receptor concentrations in endometrium from ewes treated subsequently with either progesterone for 5 days or progesterone for 5 days plus oestradiol on Days 4 and 5 of progesterone treatment. Oestradiol increased endometrial oxytocin receptor concentrations when administered on Days 4 and 5 of 5 days progesterone treatment. Progestagen pre-treatment followed by progesterone treatment for 12 days caused a large increase in oxytocin receptors and no further increase occurred when ewes were given oestradiol on Days 11 and 12, or when progesterone was withdrawn on Days 11 and 12, or these two treatments were combined. Oxytocin administration caused an increase in plasma PGFM concentrations in ewes which did not receive progestagen pre-treatment, and subsequently received progesterone treatment for 5 days and oestradiol treatment on Days 4 and 5 of progesterone treatment. Similarly treated ewes which received progestagen pre-treatment did not respond to oxytocin. Oxytocin administration also increased plasma PGFM concentrations in ewes which received progestagen pre-treatment followed by progesterone treatment for 12 days, progesterone treatment for 12 days plus oestradiol on Day 11 and 12 of progesterone treatment, progesterone withdrawal on Day 11 and 12, or progesterone withdrawal and oestradiol treatment combined. The results indicate that (1) progesterone pre-treatment affects oxytocin receptor concentrations in the endometrium and uterine responsiveness to oxytocin and (2) progesterone treatment alone for 12 days after a treatment which mimics a previous luteal phase and oestrus is sufficient to induce oxytocin receptors and increase oxytocin-induced PGF release. These results emphasize the importance of progesterone and provide information which can be used to form an hypothesis for control of luteolysis and oestrous cycle length in the ewe.
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PMID:Control of endometrial oxytocin receptor and uterine response to oxytocin by progesterone and oestradiol in the ewe. 217 61

A double-blind placebo-controlled trial was performed in 20 primigravidae to assess the physiological and clinical effects of oral mifepristone on myometrial contractility and sensitivity in the second trimester. Ten women received 600 mg of oral mifepristone and 10 women a placebo 24 h before abortion was induced in both groups, with extra-amniotic PGE2 instillation. Intrauterine pressure recordings demonstrated increased spontaneous uterine activity and increased sensitivity to PGE2 and ergometrine, but no change in oxytocin sensitivity after mifepristone treatment. There were no significant differences in PGE or PGF metabolite concentrations in peripheral maternal plasma over the 24-h study period after treatment between the mifepristone and placebo groups. The mean induction abortion interval in the mifepristone group was 512 (SD 321) min compared with 1128 (SD 606) min in the placebo group (P less than or equal to 0.02). The mechanism whereby mifepristone provokes enhanced uterine contractility and sensitivity to prostaglandins, with a reduction in abortion times, does not appear to be through endogenous production of PGE or PGF.
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PMID:The physiological and clinical effects of progesterone inhibition with mifepristone (RU 486) in the second trimester. 219 18

Two experiments were performed to determine whether arginine vasotocin (AVT) stimulates synthesis of prostaglandins (PGs) in reptilian oviducts. Homogenized oviducal tissue from female Sceloporus jarrovi in early and late pregnancy were cultured with radiolabeled (14C) prostaglandin precursor, arachidonic acid (AA). In late pregnancy, oviducts exposed to AVT exhibited a greater conversion of AA to PGF2 alpha than did controls, whereas in early pregnancy there was no difference. The conversion of AA to other prostaglandins (PGA2, PGD2, PGE2, PGI2) was not influenced by AVT. The second experiment examined whether endogenous in vitro synthesis of PGF and PGE2 from intact, pregnant oviducts was stimulated by AVT (50 ng/ml; 100 ng/ml). Both doses of AVT induced a similar, significant rise in PGF concentrations within 30 min whereas no significant increase was noted in PGE2 concentrations until 90 min after treatment. Indomethacin pretreatment blocked synthesis of both PGF and PGE2 for 30 min following AVT treatment. These data indicate that AVT induces a highly specific rise in the synthesis of PGF from the oviduct of female S. jarrovi in late pregnancy. Furthermore, the prostaglandin-stimulating effect of AVT in reptiles appears homologous with the effect of oxytocin in mammals and AVT in birds. We hypothesize that this interaction is an evolutionarily conserved relationship found in all amniote vertebrates.
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PMID:Arginine vasotocin-induced prostaglandin synthesis in vitro by the reproductive tract of the viviparous lizard Sceloporus jarrovi. 230 42

We attempted to explore possible mechanism(s) subserving the influence of oxytocin on uterine motility by studying the action of the hormone on: 1) the contractile activity of isolated rat uteri in the presence or absence of indomethacin; 2) the synthesis and release of prostaglandins (PGs) into the solution incubating the uterine tissue as well as the metabolism of labelled arachidonic acid; 3) the uptake of 45Ca2+ by uterine strips. The experiments were bone with uterine preparations isolated from spayed rats treated or not with 17-beta-estradiol. The values of isometric developed tension (IDT) and of frequency of contractions (FC) induced by oxytocin in uterine strips isolated from spayed and spayed-estrogenized rats, were not modified by indomethacin at 10(-6) M. On the other hand, uterine strips from untreated spayed rats, release into the incubating medium approximately equal amounts of PGE1, PGE2 and PGF2 alpha. The in vitro presence of oxytocin (50 mU/ml) increased significantly (p 0.05) the output of PGF 2 alpha without changing the release of PGE1 or PGE2. Uteri from spayed rats injected prior to sacrifice with 17-beta-estradiol released significantly less PGE1 and PGE2 (p less than 0.005) than preparations from non-injected animals, whereas the output of PGF2 alpha in the suspending solution remained unchanged. Following estrogenization the addition of oxytocin to preparations obtained from spayed-estrogenized rats also increased the output of uterine PGF2 alpha (p less than 0.001) without changing that of PGs E1 or E2.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Oxytocin enhances the basal release of uterine prostaglandin F2 alpha, but not that of PGE1, or of PGE2, and changes the metabolism of exogenous arachidonate, favouring the formation of prostaglandin F2 alpha and 5-HETE. Relationships with its uterotonic action and modulation by estradiol. 240 24


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