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

This experiment was designed to examine the effects of progesterone on endogenous and oxytocin-induced secretion of prostaglandin F2 alpha (PGF2 alpha) in sows. Peripheral concentrations of 13,14-dihydro-15-keto-PGF2 alpha (PGFM) were used as an indirect measure of uterine PGF2 alpha secretion. Eight sows received twice daily injections of progesterone (160 mg/injection) on d 1 to 5 after estrus. Another eight sows received comparable injections of a corn oil injection vehicle. Each sow then received i.v. injections of oxytocin (30 IU) on d 10, 12, and 15 after estrus. Concentrations of PGFM were determined in jugular venous blood samples collected at -60, -45, -30, -15, 0, 2, 5, 10, 15, 30, 45, 60, 90, and 120 min after each oxytocin injection. The mean concentrations of PGFM in samples collected before injection of oxytocin (baseline), the magnitude of the PGFM response to oxytocin, and the area under the PGFM response curve (AUC) were calculated for the three oxytocin challenges administered to each sow. Baseline, magnitude, and AUC were low on d 10 after estrus and similar for the two treatment groups. On d 12 baseline, magnitude, and AUC remained low in the control sows; however, all three response variables increased in sows that received progesterone. By d 15, all three variables were high and similar in both treatment groups. In conclusion, progesterone, administered early in the estrous cycle, seems to promote premature secretion of PGF2 alpha as indicated by the high basal concentrations of PGFM observed before injection of oxytocin on d 12.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Changes in peripheral concentrations of 13,14-dihydro-15-keto-prostaglandin F2 alpha induced by progesterone in swine. 815 31

The effect of oestradiol and progesterone concentrations on the uterine PGF2 alpha response to oxytocin was investigated by measuring 13,14-dihydro-15-keto PGF2 alpha (PGFM) secretion. One week after ovariectomy, 27 ewes were administered progestagen for 10 days followed by oestradiol for 2 days. Day 0 was designated as the time of the last 'oestrous' oestradiol injection. Six groups of ewes (n = 4) were then treated for 12 days with a high or low dose of progesterone (36 or 12 mg day-1) either alone or with a high or low dose of oestradiol (36 or 12 micrograms day-1) administered (in 1 ml of corn oil by i.m. injection, at intervals of 8 h) in a pattern designed to simulate a natural oestrous cycle profile. A control group (n = 3) was given corn oil alone. Ewes were treated with 1 microgram oxytocin (i.v.) on days 4, 8 and 12 of the simulated cycle and plasma was collected for assay of PGFM. An oxytocin-induced PGFM response occurred only on day 12, when the response was suppressed by high doses of progesterone and stimulated by high oestradiol doses. There was a significant effect of progesterone (P < 0.05) and a highly significant effect of oestradiol (P < 0.01) on the pattern of PGFM release in response to oxytocin. Low progesterone/high oestradiol stimulated the largest and most sustained increase in PGFM following oxytocin. There was a significant relationship between the oestradiol:progesterone ratio and the mean PGFM response on day 12 (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Quantitative control of oxytocin-induced PGF2 alpha release by progesterone and oestradiol in ewes. 818 82

The role of oestradiol in the control of premature luteolysis (previously shown to occur by the normal luteolytic mechanism involving PGF2 alpha and oxytocin) was investigated in anoestrous ewes induced to ovulate using GnRH (250 ng every 2 h for 24 h followed by 125 micrograms on day 0) without progesterone pretreatment. Seven ewes were administered charcoal stripped bovine follicular fluid (bFF) on days 1-5 (2 ml by s.c. injection every 8 h) together with oestradiol on days 2-4 (4 micrograms in 1 ml of corn oil by i.m. injection every 8 h). Ten ewes were treated with bFF and corn oil (as above), and ten ewes received saline and corn oil (control group). All ewes were treated with 1 microgram oxytocin (i.v.) on day 4 and plasma was collected for measurement of 13,14-dihydro-15-keto PGF2 alpha (PGFM). Blood samples were collected for measurement of progesterone and oestradiol (day--2 to 15). The ewes in the control group that responded to GnRH formed either normal (50% of ewes) or short-lived (50% of ewes) corpora lutea identified by progesterone profiles. The proportion of ewes that displayed premature luteolysis was reduced (P < 0.05) by bFF treatment alone (to 11% of ewes), and increased (P < 0.001) by bFF plus oestradiol treatment (to 100%). bFF treatment suppressed oestradiol concentrations (P < 0.01), whereas bFF plus oestradiol treatment increased oestradiol concentrations (P < 0.001) on days 1-5.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of bovine follicular fluid and exogenous oestradiol on the GnRH-induced short luteal phase in anoestrous ewes. 818 92

The oxytocin receptor inhibitor 1-deamino-2-D-Tyr-(oET)-4-Thr-8-orn-oxytocin (CAP) was infused into late pregnant sheep. Basal and oxytocin-induced prostaglandin (PG) concentrations in maternal and fetal plasma were determined. CAP had no significant effect on maternal PGFM or PGE2 or fetal PGF2 alpha, PGFM or PGE2 concentrations during late pregnancy or at term. PGF2 alpha was not detectable in maternal peripheral plasma. CAP infusion did not affect fetal well-being. Oxytocin injection to the mother caused a significant, dose-dependent, increase in maternal plasma PGFM concentrations but did not alter maternal PGE2 concentrations or fetal PGF2 alpha and PGE2 concentrations. The increase in maternal PGFM concentrations brought about by oxytocin injection was decreased during intrauterine infusion of CAP over the range of 12.5-100 micrograms/min. A rationale for the use of oxytocin receptor blockade for the prevention of premature labor is thus provided.
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PMID:Oxytocin receptor blockade and prostaglandin release in late pregnant sheep. 818 13

This is a study on the correlation of maternal serum oxytocin and prostaglandin F2 alpha (PGFM) levels with sonographically measurable changes in the cervix and the internal cervical os in patients with preterm labor. Oxytocin levels significantly correlate (P = 0.03) with the width of the internal os and the PGFM values significantly correlate with the length of the cervix (P = 0.008). An increase in the oxytocin level resulted in a measurable widening of the internal os and an increase in the prostaglandin level resulted in a measurable shortening of the cervix.
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PMID:Serum prostaglandin F2 alpha (PGFM) and oxytocin levels correlate with sonographic changes in the cervix in patients with preterm labor. 832 18

The objective of this study was to clarify the role of oestradiol in luteal function by examining its effect on the oxytocin stimulation of 15-keto-13,14-dihydro-prostaglandin F2 alpha (PGFM) concentrations in cyclic mares. In the first experiment, three groups of mares (4 per group) were given a bolus injection of 17 alpha-oestradiol (1 mg), oestradiol (1 mg) or vehicle on days 7, 9, 11, 13 and 15 of the cycle. Six hours later the mares were challenged with 10 iu oxytocin intravenously and frequent blood samples were taken from 15 min before to 15 min after for measurement of PGFM. Results showed a significant stimulatory effect of oestradiol (five times greater than controls at day 11; P < 0.05), but not of 17 alpha-oestradiol, on the oxytocin stimulation of PGFM. As a relatively large dose was given systemically in this experiment, a second experiment was performed to introduce a dose that was more physiological into the uterus. Small Silastic spheres (1 cm diameter) were impregnated with or without oestradiol at a concentration that gave a release rate similar to that of embryos at day 12 (10 ng h-1). These were inserted (one per mare) into the uterus of two groups of mares (five per group) on day 7. The mares were challenged with oxytocin on days 9, 11, 13 and 15 of the cycle and blood samples were taken as before for determination of PGFM. The results showed that oestradiol enhanced (four times greater than controls at day 13; P < 0.05) the oxytocin stimulation of PGFM concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of oestradiol on oxytocin-stimulated prostaglandin F2 alpha release in mares. 834 53

The bovine CL is one of the sites for the production of prostaglandins (PG). Although many in vitro models, mainly using dispersed luteal cell incubations, have shown the variety of CL responses to PGs (luteotropic, no effect, or luteolytic), the functional role of luteal PGs in cattle remains to be elucidated. Therefore, the aim of the present study was to examine the effects of PGs with respect to progesterone (P4) and oxytocin (OT) release from the bovine CL in vitro (Days 8-12 of the estrous cycle) via a microdialysis system (MDS), in which intact cell-to-cell contact exists. Thirty-minute perfusion with PGF2 alpha, PGE2, and PGI2 (10(-10)-10(-5) M) induced significant, but different, acute effects. PGF2 alpha and PGE2 clearly stimulated hormone (P4 and OT) release, while PGI2 slightly inhibited hormone secretion during infusion at low doses but stimulated secretion at 10(-6) and 10(-5) M concentrations. Additionally, catabolized PGF2 alpha and PGI2 (13,14-dihydro-15-keto-PGF2 alpha [PGFM] and 6-keto-PGF1 alpha, respectively) induced responses different from those of the original PGs; both PGFM and 6-keto-PGF1 alpha at low doses weakly inhibited P4 release, but at 10(-5) M concentration stimulated release. Phorbol 12-myristate 13-acetate (TPA), a potent stimulator of the protein kinase C (PKC) system in bovine luteal cells, stimulated P4 and OT release when administered alone. Pre-exposure with TPA (10(-9) M) for 2.5 h resulted in an increase in the stimulative potency of PGF2 alpha and PGI2, but not of PGE2.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Acute actions of prostaglandin F2 alpha, E2, and I2 in microdialyzed bovine corpus luteum in vitro. 837 69

On days 13 and 14 after oestrus (day 0) oxytocin and 13,14-dihydro-15-keto-prostaglandin (PG)F2 alpha (PGFM) concentrations were measured in jugular plasma of hysterectomised sheep with or without systemic treatment with the PG cyclo-oxygenase inhibitor indomethacin (4 mg kg-1 three times a day on days 12, 13 and 14 subcutaneously. Pulsatile increases of oxytocin were observed in both untreated and treated sheep with mean (+/- SD) peak heights of 18.4 +/- 9.6 pg ml-1 (n = 11) and 23.5 +/- 9.4 pg ml-1 (n = 8), respectively; these means were not significantly different. Plasma concentrations of PGFM remained consistently low in both groups (under 100 pg ml-1) with no significant peaks observed. The data suggest that PGF2 alpha may not be the only stimulus for the release of luteal oxytocin, or that there may be a contribution by the posterior pituitary to oxytocin secretion during the luteal phase of the ovine oestrous cycle.
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PMID:Pulsatile release of oxytocin after suppression of prostaglandin synthesis in hysterectomised ewes. 837 11

The metabolism of arachidonic acid (AA) by caruncular and allantochorionic tissues and its regulation was studied in normal cows (n = 13) and those with retained fetal membranes (RFM; n = 9). Tissues were taken via the vagina about 6 hours postpartum and incubated for 6 hours in minimum essential medium containing tritiated AA alone or in the presence of oxytocin, platelet activating factor (PAF), epidermal growth factor (EGF) or ionophore calcium (A23187). The metabolites of AA were separated by reverse phase-high pressure-liquid chromatography. Tissue concentrations of prostaglandin F2 alpha (PGF2 alpha) and prostaglandin E2 (PGE2) and plasma 13,14-dihydro-15-keto-PGF2 alpha (PGFM) concentration were also measured by radioimmunoassay. For caruncular tissue, less thromboxane B2 (TXB2) and more 6-keto prostaglandin F1 alpha (PGIM) was synthesized in tissue from the animals with RFM than in the controls. Oxytocin, PAF, EGF and A23187 increased only PGIM production in the control animals; A23187 also decreased TBX2 synthesis. For the allantochorion, more PGE2, leukotriene B4 (LTB4) and PGIM and less TXB2, PGF2 alpha and hydroxyecosatetranoic acids (HETE) was synthesized in tissue from cows with RFM than from animals that delivered normally. All of the substances used in this study increased PGIM, PGF2 alpha and LTB4 and decreased TXB2 production by the allantochorionic tissue in control animals. The metabolism of AA by the allantochorionic tissue seems quantitatively under hormonal control. The metabolism of AA at the level of both maternal and fetal components of the placenta in cows with RFM differed from that seen in animals that expelled the membranes normally.
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PMID:Metabolism of arachidonic acid by caruncular and allantochorionic tissues in cows with retained fetal membranes (RFM). 838 Sep 36

Two experiments investigate the effects of oxytocin and progesterone on premature luteolysis in ewes. In Expt 1, 20 anoestrous ewes were induced to ovulate by multiple injections of GnRH (250 ng i.v. every 2 h for 24 h) followed by a bolus injection of GnRH (125 micrograms, i.v.). Ten ewes received a continuous infusion of oxytocin from the day after the GnRH bolus injection and the other ten ewes were infused with saline. Oxytocin infusion had no significant effect on the proportion of ewes with short luteal phases (P > 0.05). All ewes that had luteal phases of normal duration from either group (n = 9) exhibited a transient increase in plasma concentrations of progesterone 2 h after insertion of the pump. In Expt 2, 25 anoestrous ewes were treated with GnRH as in Expt 1. Five ewes were pretreated with progestagen for 11 days and ten ewes received progesterone (12 mg, i.m.) 24 h after the bolus injection of GnRH. All animals received an oxytocin injection (1 microgram, i.v.) on day 4 after the GnRH bolus. All five ewes that were pretreated with progestagen had normal luteal function and none exhibited a 13, 14-dihydro-15-keto PGF2 alpha (PGFM) response to oxytocin. None of the ten ewes injected with progesterone had a normal luteal phase and six ewes exhibited a PGFM response to oxytocin. Four ewes in the control group had normal luteal function and three had short luteal phases. It is concluded that (1) administration of oxytocin from about the time of ovulation does not prevent premature luteal regression; (2) a transient increase in progesterone at about the time of ovulation is associated with luteal phases of normal duration; (3) a more extended exposure to progesterone at about the time of ovulation prevents normal luteal function and may inhibit luteinization and (4) pretreatment with progesterone prevents luteolysis by reducing the uterine response to oxytocin early in the luteal phase.
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PMID:Effects of exogenous oxytocin and progesterone on GnRH-induced short luteal phases in anoestrous ewes. 866 46


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