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

All uterine tissues as well as the fetal membranes and the placenta can form prostaglandins from endogenous precursors in vitro but it is not clear which of the tissues is the main site for the increase in PGF2 alpha production during human parturition. To examine this question, we measured plasma prostaglandin levels before and at intervals after expulsion of the fetus, placenta, and membranes. The concentration of PGFM at the beginning of the second stage of labor was significantly higher than before the onset of labor. Five minutes after the birth of the infant, the concentration had doubled. Thirty minutes after the expulsion of placenta and membranes, plasma PGFM had fallen to the levels at full dilatation; two hours postpartum it was still significantly raised over levels before labor. Since the halflife of PGFM in the circulation is about 7 minutes, these findings indicate that the uterine tissues are important sources of PGFM during labor. In contrast, endogenous oxytocin levels, which were significantly raised over control levels at the second stage of labor, did not change during the third stage, and declined postpartum to control levels. Oxytocin infusion did not influence PGFM levels at 5 and at 30 minutes postpartum, but raised them at 2 hours.
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PMID:The origin of circulating 13,14-dihydro-15-keto-prostaglandin F2 alpha during delivery. 716 13

Plasma concentrations of neurophysin I/II (N-I/II), 13,14-dihydro-15-keto-prostaglandin F (PGFM) and progesterone were measured by radioimmunoassay in plasma samples collected from four sheep at hourly intervals between 0700 and 1900 h from Days 12-17 of the estrous cycle. Plasma samples were also collected from a fifth sheep at 2-hourly intervals during Days 12-16 of the cycle. In all sheep, intermittent surges in the plasma concentrations of PGFM and N-I/II occurred during the period of luteal regression. On at least one occasion in each sheep a surge in the plasma concentration of N-I/II was observed coincident with a rise in PGFM concentrations. In general, the highest levels of N-I/II were observed early in luteolysis (Days 13-14 of the cycle) while the corresponding levels of PGFM in plasma were maximal around Day 15 when luteolysis was well advanced. It is suggested from this temporal data that oxytocin, which is considered to be released in association with N-I/II, may play an important role in ovine luteolysis by stimulating the secretion of prostaglandin F from the uterus during days 13-15 of the estrous cycle.
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PMID:Temporal relationship between plasma concentrations of 13,14-dihydro-15-keto-prostaglandin F and neurophysin I/II around luteolysis in sheep. 719 Nov 32

Peripheral plasma concentrations of oxytocin, 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM), progesterone and LH were determined at 3 hourly intervals during the oestrous cycle (n = 3) and in early pregnancy (n = 4) in sheep. The progesterone and LH concentrations showed that the cycling ewes were sampled during the periods of luteal regression (decreasing progesterone concentrations), the preovulatory gonadotrophin surge and the beginning of the next luteal phase (increasing progesterone concentrations). The pregnant ewes had basal LH concentrations and luteal phase concentrations of progesterone (greater than 1ng/ml after day 5 following mating) throughout the whole of the sampling period. Oxytocin concentrations in the non-pregnant ewes decreased around the time of luteal regression to reach low concentrations (mean concentrations of approximately 18pg/ml) during the preovulatory period and then increased after the preovulatory surge. PGFM concentrations exhibited a pulsatile pattern with increasing concentrations as progesterone levels fell. In the pregnant ewes oxytocin concentrations gradually fell until approximately 16 days post-mating (approximately 7-8pg/ml). The magnitude of the pulses in PGFM concentrations were also lower than in the cycling ewes. These results demonstrate that the increased concentrations of PGFM which are found during the period of luteal regression are not caused by increased peripheral concentrations of oxytocin.
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PMID:Temporal relationships between peripheral plasma concentrations of oxytocin, progesterone and 13,14-dihydro-15-keto-prostaglandin F2 alpha during the oestrous cycle and early pregnancy in the ewe. 730 65

Maternal peripheral plasma levels of 13,14-dihydro-15-keto-prostaglandin F (PGFM) were measured in 16 women following amniotomy performed for the induction of labour at term. After 5 1/2 hours, seven patients were in established labour (Group I) but the remaining nine patients required an intravenous infusion of oxytocin (Group II). An initial rapid rise in PGFM concentrations within five minutes of amniotomy occurred in all women and, therefore, the onset of labour does not appear to be a direct consequence of this initial increase. In Group I there was a significant increase in PGFM concentrations between five and 30 minutes after amniotomy and from 30 minutes to the time at which the last sample was collected; these later rises were associated with the onset and progress of labour in these women. These increases in PGFM concentrations did not occur in patients in Group II. The reason for this difference in response to amniotomy is as yet unclear.
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PMID:The relation between the release of prostaglandins at amniotomy and the subsequent onset of labour. 730 75

The rise in peripheral plasma levels of 13,14-dihydro-15-keto-prostaglandin F (PGFM) following amniotomy has now been shown to be maximal within five minutes of the procedure, and levels remain elevated for at least 30 minutes. There was no change in plasma oxytocin levels with amniotomy and therefore a local mechanism for prostaglandin release has been postulated.
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PMID:Release of prostaglandins after amniotomy is not mediated by oxytocin. 736 88

Levels of the major circulating metabolite of prostaglandin F-2 alpha, 13, 14 dihydro-15-oxo-prostaglandin F-2 alpha (PGFM) were measured during the induction of foaling using small (2.5-10 iu) intravenous doses of oxytocin. PGFM levels rose rapidly in all animals within 15 min of injection and were associated with typical signs of second stage labour. Because these small doses of oxytocin are effective in successfully triggering parturition it is suggested that higher doses (40-120 iu) used to induce birth in other studies are unnecessary and could be potentially dangerous to the foetal foal.
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PMID:Low doses of oxytocin can induce foaling at term. 737 16

Mated cows that subsequently undergo luteolysis have significantly lower plasma concentrations of progesterone than do cows in which pregnancy is maintained. Two groups of ovariectomized cows were treated with progesterone and oestradiol to recreate luteal phases exhibiting the extremes of plasma concentrations of progesterone (6.0 +/- 0.4 and 12.4 +/- 0.8 ng ml-1) normally seen in intact cows. The effect of this difference in progesterone on the development of the luteolytic signal was determined by monitoring the basal and oxytocin-stimulated plasma concentrations of the principal metabolite of prostaglandin F2 alpha' PGFM on days 12-16 of the simulated luteal phases. Basal PGFM concentrations were similar in the low and high progesterone groups on all days. The mean plasma concentration of PGFM showed a larger increase following oxytocin in the low progesterone group on days 13 and 14 (P < 0.05) and on days 15 and 16 (P < 0.1). These results demonstrate that a low plasma concentration of progesterone results in the development of a stronger luteolytic signal, and provide an explanation for the fact that cows with lower plasma concentrations of progesterone are more prone to embryo loss.
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PMID:Progesterone inhibition of the development of the luteolytic signal in cows. 763 90

We have investigated the effects of oestradiol-17 beta on the development of the luteolytic signal (prostaglandin F2 alpha (PGF2 alpha) release to an oxytocin challenge) using a steroid-treated ovariectomised cow model. Long-term ovariectomised cows were pre-treated with progesterone for 14 days followed by oestradiol-17 beta for 2 days to induce oestrus (day 0), and were then treated for a further 16 days with physiological doses of progesterone and oestradiol-17 beta to simulate a luteal phase. On day 11 oestradiol was either withdrawn (low group; n = 4), maintained (normal group; n = 4) or increased (high group; n = 4), generating mean (+/- S.E.M.) plasma concentrations of oestradiol from days 12-16 of 0.9 +/- 0.1, 2.3 +/- 0.4 and 3.7 +/- 0.2 pg/ml respectively. Basal and oxytocin-stimulated PGF2 alpha secretion was monitored by measuring concentrations of the principal metabolite of PGF2 alpha, 13,14-dihydro-15-keto PGF2 alpha (PGFM), in plasma samples collected before and after daily i.v. injection of 50 IU oxytocin from days 12-16. Basal PGFM was unaffected by the level of oestradiol treatment. In the normal group significant rises in plasma PGFM were seen following oxytocin on days 12, 13 and 14 (P < 0.05) as well as days 15 and 16 (P < 0.01). In the low group significant elevations in PGFM were only seen on days 15 and 16 (P<0.05), and were smaller (P<0.05) than those seen in the normal group.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of the level of oestradiol on oxytocin-induced prostaglandin F2 alpha release in the cow. 779 24

The aim of this study was to examine whether prostaglandins are involved in the effects of noradrenaline on corpus luteum (CL) function. To establish an effective dose of indomethacin (INDO) to prevent prostaglandin synthesis, different doses (120, 180, 240 and 300 mg) of drug were infused for 30 min on days 17-18 of the estrous cycle in four heifers and followed with 50 IU of OT. Plasma concentrations of 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) were measured, both to illustrate the concentrations of all prostaglandins and to establish the effective dose of INDO that can effectively block prostaglandins synthesis. In Experiment 2, on days 10-12 of the cycle, heifers (n = 6) were infused in a Latin square design with 4 mg of noradrenaline (NA) and pre-treated with 120 mg of INDO or with saline. In both cases, NA did stimulate progesterone and ovarian oxytocin secretion. We conclude that NA affects secretory function of the CL independently of prostaglandins.
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PMID:Noradrenaline affects secretory function of corpus luteum independently on prostaglandins in conscious cattle. 797 75

The control of temporal changes in oxytocin receptor concentrations and oxytocin-induced 13,14-dihydro-15-keto PGF2 alpha (PGFM) release was examined in ewes. One week after ovariectomy, 36 ewes were administered fluorogesterone acetate for 10 days followed by oestradiol (3 x 16 micrograms day-1) for 2 days (pretreatment cycle). Day 0 was designated as the time of the final 'oestrous' oestradiol injection. Ewes were then treated for up to 12 days with progesterone (24 mg day-1 maximum) with or without oestradiol (both hormones administered in 1 ml of corn oil i.m. at 8 h intervals) in a pattern known to simulate natural plasma profiles of the oestrous cycle. The three treatments were zero oestradiol, low oestradiol (12 micrograms day-1 maximum), and high oestradiol (36 micrograms day-1 maximum). Subgroups of four ewes from each treatment group were given 1 microgram of oxytocin (i.v.) on day 10, 11 or 12 of the simulated cycle, and endometrial oxytocin receptor concentrations were determined in samples collected within 3 h of oxytocin administration. On day 10 only one ewe in each group exhibited a PGFM response to oxytocin, and the mean response was unaffected by the concentration of oestradiol administered. On days 11 and 12 there was a significant effect of oestradiol concentration (P < 0.05) on the pattern of PGFM release in response to oxytocin, the high oestradiol concentration causing a rapid increase in the concentration of PGFM following oxytocin administration. On day 12 the oestradiol concentration was positively correlated with the PGFM mean response (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Oestradiol concentration and the development of the uterine oxytocin receptor and oxytocin-induced PGF2 alpha release in ewes. 802 65


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