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

Uterine responses to vasopressin and oxytocin were monitored in non-pregnant and 3- or 6-8-day-pregnant rabbits by recording the intrauterine pressure. Oxytocin stimulated uterine activity in all groups, but the effect of vasopressin was stimulatory in non-pregnant animals, inhibitory in those 3 days post coitum and weakly stimulatory in those later in pregnancy. Inhibition of prostaglandin (PG) synthesis, by the administration of indomethacin, reduced the spontaneous uterine activity as well as the responses to oxytocin and vasopressin in the non-pregnant rabbits, but had little effect in the pregnant animals. During infusion of PGF-2alpha, PGE-1 or PGE-2 in 6-8-day-pregnant rabbits, the stimulatory response to vasopressin, although slight before the infusion, was inhibited whereas the stimulatory response to oxytocin remained virtually unchanged. The results suggest that vasopressin and oxytocin under certain hormonal conditions, are able to activated the uterine contractions by mechanisms in which the involvement of PG is not obligatory.
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PMID:Differences in the effects of vasopressin and oxytocin on rabbit myometrial activity and a possible mediation of prostaglandins. 59 88

Oxytocin and PGE2 (prostaglandin D 2) were administered to 2 groups of 20 women, 40 weeks pregnant, in order to induce labor. Labor duration was significantly shorter in the PGE2 group (2 hrs., 36 mins.) than among the oxytocin group (3 hrs., 26 mins.). The peak uterine pressure for PGE2 patients was significantly lower; the baseline uterine pressure was significantly greater, indicating more even labor contractions. There was a highly significant correlation between the interval from administration to the initial contraction and the total labor duration (p .005) and between the interval from administration to the beginning of regular contractions and the total labor duration (p .01) among the PGE2 patients. There was also a highly significant correlation (p .01) between the dosage/kg until the initial contraction and the total pregnancy duration and between the dosage/kg until the beginning of regular contractions and the total pregnancy duration for PGE2 patients. PGE2 patients showed a significantly faster cervical dilation (.05 p .1) and a significantly shorter interval between dilatation and delivery (p .05). PGE patients also showed a significantly shorter interval between the initial contractions and delivery and between the beginning of regular contractions and delivery. Also, a significant correlation between cervical dilatation and delivery was demonstrated among PGE2 patients. A significant correlation between cervical dilatation and the beginning of contractions was established only for oxytocin patients.
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PMID:[Comparison of labour induction with intravenous prostaglandin E2 and intravenous oxytocin (author's transl)]. 97 23

Contractility parameters (uterine activity, contraction interval, amplitude, and frequency of contractions) were analyzed quantitatively during the active phase of first-stage of labour in 60 clinically normal term nulliparae with spontaneous or induced labour. Inductions were surgical (amniotomy alone) or by amniotomy combined with either intravenous oxytocin or prostaglandin administered intravenously (PGF 2alpha or PGE 2) or orally (PGE 2).
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PMID:Uterine contractility in spontaneous and induced labour. 98 99

A clinical team in the Dept. of Obstetrics and Gynecology of the Albert Einstein College of Medicine investigated the effects of several prostaglandin compounds of human pregnancy. Women between 8 to 20 weeks gestational age had pregnancy termination through: 1) intraamniotic PGF2alpha (prostaglandin F2a) administration (n=20, 15.9 + or - 0.6 weeks pregnant, 1.4 + or - 0.4 parity); 2) extraovular PGF2a administration (n=20, 13 + or - 0.3 weeks gestation); 3) intramuscular 15-methyl PGF2a administration; 4) vaginal suppositories of PGE2 (n=110 women, 1.45 + or - 0.17 parity, 15.4 + or - 0.3 gestational weeks); and 5) induction of term labor through PGF2a and PGE2 administered orally, intravenously, vaginally, and extraovularly. In the 1st group, the 20 women aborted in 16.5 + or 2.1 hours with an average total dose of 24.3 + or - 1.1 mg. In the 2nd group, the 20 women aborted in 17.9 + or - 2.9 hours with 11 + or - 1.8 mg PGF2a. The 24-hour cumulative abortion rate was 83%. In both intraamniotic and extraovular groups, prostaglandin side effects were noted in 25% to 70% of the women. Incidence of retained placentas was also high. In the 3rd group, abortion did not follow a predictable pattern and side effects occurred in virtually all women, making this approach unacceptable as a therapeutic method. The vaginal suppositories resulted in a mean abortion interval of 14.12 + or 0.7 hours with an average total dose of 78.3 + or - 0.12 mg. Induction of term labor using PGF2a and PGE produced results which are not superior to those of intravenous oxytocin in term pregnancies, possibly because of the biophysical properties of the term uterus. Prostaglandins appear to be effective abortifacient agents with minimal material risk, and are most effective when administered intraamniotically, extraovularly, and paracervically. The chemistry and pharmacology of prostaglandins are briefly described.
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PMID:Prostaglandins in conception control. 108 Feb 45

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

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

Oxytocin is synthesized in the granulosa-derived large cells of the ruminant corpus luteum from a gene which is dramatically up-regulated in the first few days after ovulation. In this work, the regulation of granulosa and luteal cells by prostaglandins and insulin (or insulin-like growth factor-I; IGF-I) has been explored by comparing their effects on oxytocin and progesterone production in cell culture. In granulosa cells, chronic exposure to insulin (17 nmol/l) stimulated luteinization as indicated by increased release of oxytocin and progesterone. Prostaglandin F2 alpha (PGF2 alpha) alone had little effect, but synergized with insulin (or IGF-I) to increase the release of both these hormones. In direct contrast, insulin-stimulated oxytocin production by luteal cells was inhibited by PGF2 alpha. The half-maximal dose (EC50) for PGF2 alpha action in both cell preparations was similar (10-100 nmol/l). Dose-response studies revealed that PGF2 alpha increased the potency of insulin in granulosa cells (EC50 for insulin-stimulation of oxytocin release reduced from 141 to 13 nmol/l by 1 mumol PGF2 alpha/l), but not in luteal cells. Insulin-stimulated oxytocin release from granulosa cells was also synergistically increased by PGE1, PGE2 and forskolin, suggesting this effect to be mediated by adenylate cyclase-coupled PGE receptors. The results reveal that the effects of prostaglandins on oxytocin release are dependent on both the developmental stage of the target tissue and on the presence of other regulators of cellular differentiation. Moreover, they suggest that the increase in responsiveness to insulin and IGF-I, which appears to accompany luteinization in the cow, may be an effect of prostaglandins produced locally during the peri-ovulatory period.
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PMID:Chronic regulation of ovarian oxytocin and progesterone release by prostaglandins: opposite effects in bovine granulosa and early luteal cells. 240 66

A study was designed to see if incorporating intracervical administration of prostaglandin could affect the outcome of postdate pregnancies. All patients with verified dates, at least 41 6/7 weeks pregnant and enrolled in an antepartum testing schedule were randomized in a double-blind fashion to receive either 0.5 mg of prostaglandin E2 (PGE2) suspended in methylcellulose or a placebo of the gel alone. The gel was inserted directly into the cervical canal after the patient had a reactive/negative contraction stress test. The patient was then observed on an external fetal monitor for an hour before going home. A total of 23 patients received PGE2, and 20 received the placebo. Results were analyzed for the following: change in the Bishop score, lag time from dosage to delivery, spontaneous versus induced labor, cesarean section rate, length of labor and neonatal outcome. There were no significant differences between the groups except in the incidence of patients going into labor within 72 hours. The results indicate that, in general, 0.5 mg of intracervical PGE administered at greater than or equal to 41 6/7 weeks without subsequent oxytocin induction of labor did not appear to significantly alter the obstetric outcome.
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PMID:Intracervical prostaglandin in postdate pregnancy. A randomized trial. 240 38

1. Membrane currents were recorded from voltage clamped Xenopus laevis oocytes, still surrounded by follicular cells, theca and enveloping inner ovarian epithelia (ovarian follicles). 2. Superfusing follicles with frog Ringer solution containing E-series prostaglandins (PGE1 or PGE2) or oxytocin (0.5-2 microM) generated slow membrane currents arising from an increase in membrane conductance to K+. 3. Follicles taken from different frogs varied greatly in responsiveness to PGE and oxytocin. For example, enclosed oocytes with good sensitivity to prostaglandins responded to 1 nM-PGE, whereas follicles from some frogs failed to respond at 5 microM. 4. Oocytes with good responsiveness to PGE also produced K+ currents to PGA1, PGA2, PGB1, 11-deoxy-PGE1 and 11-beta-PGE2, whereas PGF2 alpha, PGI2, PGD2 and 8-iso-PGE1 generally failed to elicit membrane currents. 5. Responses to PGE and oxytocin were mimicked by the adenylate cyclase activator forskolin or by intraoocyte pressure injection of cyclic nucleotides. Responses were potentiated by the phosphodiesterase inhibitors theophylline and 3-isobutyl-1-methylxanthine (IBMX). In IBMX (0.5 mM), human atrial natriuretic factor (ANF) (10-60 nM) elicited a similar K+ conductance. This all implied that cyclic nucleotides played a role in the receptor-channel coupling mechanism of these responses. 6. Defolliculating oocytes effectively abolished responses to prostaglandins, oxytocin and ANF, suggesting that the currents arise in follicular cells. 7. The responses of PGE, oxytocin and ANF thus resembled currents elicited by catecholamines, adenosine, gonadotrophins and vasoactive intestinal peptide (VIP). However, PGE, oxytocin and ANF responses were not blocked by catecholaminergic or purinergic antagonists. Moreover, when comparing follicles isolated from different frogs, the sensitivity to PGE and oxytocin varied independently of that to gonadotrophin or VIP. These experiments suggest that Xenopus ovarian follicles contain specific and distinct receptors for PGE, oxytocin and ANF. 8. Acetylcholine attenuated the cyclic nucleotide-mediated K+ responses, including currents elicited by PGE, oxytocin and ANF. Attenuation was not dependent on, or mimicked by, activation of the inositol phosphate-diacylglycerol messenger pathways located in the oocyte itself, nor was it appreciably blocked by loading follicle-enclosed oocytes with 0.1-1.5 mM-EGTA.
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PMID:Membrane currents elicited by prostaglandins, atrial natriuretic factor and oxytocin in follicle-enclosed Xenopus oocytes. 248 34

Blood samples were collected frequently from permanent catheters placed in the aorta and caudal vena cava of 36 heifers in order to monitor the release pattern of LH, FSH, progesterone, oestradiol-17 beta, oxytocin, PGF-2 alpha, PGE-2 and PGI-2 (determined as its 6-keto-PGF-1 alpha metabolite). The frequency of secretory bursts of both gonadotrophins and progesterone was similar in early pregnant and cyclic animals, whereas the amplitude of LH and progesterone increased between 2 and 4 weeks of gestation. Concentrations of circulating oestradiol-17 beta and oxytocin were already lower at Days 4-7 in pregnant than in cyclic animals. Oestradiol-17 beta originated after Day 14 from the uterus rather than the ovary. A sustained release of oxytocin most probably from the posterior pituitary gland and a concomitant decrease of progesterone occurred in about two-thirds of pregnant animals during Days 19-23. Insemination could induce releases of PGF-2 alpha lasting up to 2 h. In addition, basal concentrations of PGF-2 alpha during the first 6 days after oestrus were approximately 2-fold higher in inseminated than in non-inseminated cyclic heifers. A parallel increase of PGF-2 alpha and PGI-2 occurred between Days 30 and 33 of gestation. Early embryonic mortality resulted, at least up to Day 35, in 4-7 concomitant secretory bursts of PGF-2 alpha and luteal oxytocin. There was a delay of 20-26 h between the first and second release. The present results from in-vivo experiments point towards major endocrine changes in cattle within a few days after conception, resulting in an early inhibition of follicular oestradiol-17 beta and luteal oxytocin facilitating the suppression of luteolytic releases of PGF-2 alpha.
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PMID:Sequences of pituitary, ovarian and uterine hormone secretion during the first 5 weeks of pregnancy in dairy cattle. 250 92


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