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

Intravenous bolus injections of pig relaxin which produced short-lived peaks of the hormone equivalent in concentration to those observed at term promptly rendered the uterus almost totally quiescent and the inhibition persisted for about 2.5 h. During this time the uterus remained responsive to oxytocin. The main effect of relaxin was to reduce the frequency of intrauterine pressure cycles rather than the amplitude. In contrast progesterone, which also inhibited myometrial activity, took between 6 and 24 h to exert its maximum effect by reducing both amplitude and frequency of IUP cycles and it also abolished the responsiveness of the myometrium to oxytocin. Its actions were reversible but recovery took between 54 and 140 h. Oestradiol benzoate had no significant effect on myometrial activity in 21 out of 26 treatments. At 24 h after the 5 remaining treatments, however, myometrial activity was virtually zero. No evidence was obtained of a biphasic effect of oestradiol on myometrial activity as reported for the rat and ewe. This work demonstrates that purified pig relaxin is an active myometrial inhibitor in the oestrogen-treated ovariectomized non-pregnant pig in vivo.
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PMID:Relaxin and progesterone are myometrial inhibitors in the ovariectomized non-pregnant mini-pig. 394 91

Plasma relaxin levels were measured in animals at different stages of lactation and related to the amount of nuzzling and suckling behavior exhibited by the piglets. Only in some acute suckling episodes was relaxin secreted rapidly and episodically in spite of normal piglet and sow behavior and interaction. However, when the piglets were removed from the dams 6 h before suckling, the sows were very restless and the relaxin response to suckling was delayed. Oxytocin injection in lactating but nonsuckled sows caused an episodic secretion of relaxin similar to suckling itself. The source of relaxin in the lactating sow may be the old corpus luteum, since progesterone levels increased acutely, somewhat reflecting the profile of relaxin increase over the suckling episode.
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PMID:Plasma relaxin levels during suckling and oxytocin stimulation in the lactating sow. 405 30

In a randomised double-blind trial 10 of 30 patients given 2 mg of intravaginal purified porcine relaxin on the evening before surgical induction of labour went into labour before the proposed induction. Of 30 control patients, none went into labour. Of the 30 patients treated with relaxin, 25 had improved cervical scores after treatment and significantly fewer required augmentation in labour with intravenous oxytocin than the control group. Administration of relaxin was associated with very little increase in uterine activity and no side-effects. The trial shows that exogenous relaxin causes cervical ripening and can initiate parturition. Endogenous relaxin may have a similar role.
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PMID:Ripening of the human cervix and induction of labour with purified porcine relaxin. 610 76

Although the ovarian production of sex steroids is of obvious physiological importance, recent studies suggest that peptides such as oxytocin, relaxin and inhibin are also synthesized in the ovary. We report here the presence of immunoreactive (ir) beta-endorphin, ir-adrenocorticotropic hormone (ACTH) and presumptive high molecular weight forms of both in extracts of sheep ovary, consistent with ovarian production from a common precursor. Our findings suggest that beta-endorphin and ACTH are produced and secreted by the follicular cells, and that their production may be related to the oestrous cycle.
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PMID:Immunoreactive beta-endorphin in sheep ovary. 630 36

This work reviews the evolution of cervical ripening procedures and discusses the most effective current techniques. Current knowledge of the process of spontaneous ripening of the cervix is briefly assessed, but the review concentrates on methodological aspects and the clinical results of preinduction cervical ripening. The historical development of mechanical and pharmacologic ripening procedures is examined, including enzymes, oxytocin, relaxin, corticosteriods, estrogens administered parenterally or locally, and prostaglandins (PGs) administered intravenously, orally, locally, and intravaginally. 3 effective procedures for preinduction cervical ripening are identified and described in greater detail: the catheter technique and local and vaginal administration of PGs. The extraamniotic catheter technique is simple, effective, and safe and is recommended for patients with not totally unripe cervixes and for whom PGs are unavailable or contraindicated. Single-dose extraamniotic instillation of PGE2 in Tylose gel was found to be highly effective for priming the unfavorable cervix before conventional labor induction. In some patients the procedure induces labor. The technique is easy to use, well accepted by the woman, and safe when applied appropriately to carefully selected patients. PGF2alpha gel has been less thoroughly studied. Electronic monitoring at the ripening stage is recommended for patients at risk, and even in low-risk cases much larger series will require study before conclusions can be reached about safety. Injection of PG gel into the cervical canal is less invasive than extraamniotic instillation, but no definite conclusions about its safety are possible due to small series and dissimilar clinical protocols. Pericervical administration of PGE2 and PGF2 alpha and intracervical and intraamniotic tablets of PGE2 are briefly assessed. Adoption of the intravaginal route has been a major step in the development of ripening techniques. 3 types of media have been studied: a gel, suppository, and tablets. Simplicity of administration and lack of invasiveness are advantages of the techniques, but uterine overstimulation is a danger because of the large doses required.
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PMID:Preinduction cervical ripening. 634 63

Changes in plasma 15-keto-13, 14-dihydro-prostaglandin F2 alpha were monitored at frequent intervals before, during and after spontaneous deliveries (three mares) and foalings induced by oxytocin (eight mares). No evidence of increased concentrations of the prostaglandin metabolite was observed in the final 10 days of gestation. In spontaneously delivering mares, there was a marked increase from 3 ng/ml at -125 mins to 18 ng/ml at -65 mins to the highest observed value of 182 ng/ml at 20 mins pre-partum. Following delivery, concentrations declined rapidly to around 0.2 ng/ml. Further release of prostaglandins was seen on Days 1 and 3 post partum. In oxytocin induced mares, maximal concentrations of about 100 ng/ml were observed to occur very close to the time of delivery. Large increases were observed as early as 2 mins following oxytocin injection. The significance of these findings is discussed in relation to parturient and post parturient events and changes in levels of the hormone relaxin during the same period.
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PMID:Concentrations of 15-keto-13, 14-dihydro-prostaglandin F2 alpha in the mare during spontaneous and oxytocin induced foaling. 659 93

The effects of relaxin on contractility and membrane potential of the longitudinal and circular smooth muscle layers of the uterus have been studied in vitro using oestrogen-treated, non-pregnant rats and pregnant rats. Relaxin decreased the amplitude of contractions induced by electrical stimulation of longitudinal myometrium by decreasing the duration of the bursts of action potentials. This effect was transient and tachyphylaxis always developed and was observed following injection of steroids and up to day 17 of pregnancy. There was no inhibition of tissues from rats from day 18 of pregnancy to term. The peptide had no effect on resting membrane potential, space constant or time constant. Action potentials recorded from circular myometrium of non-pregnant rats pre-treated with oestrogen consisted of an initial spike or short burst of spikes followed by a prolonged plateau of depolarization. Spontaneous action potentials and associated contractions were abolished within 2 min of exposure to relaxin (10(-8) g/ml) while contractions of much smaller amplitude could be evoked with depolarizing current pulses. This effect was associated with depression of the plateau component of the action potential whereas the spike component was left intact. Relaxin had no effect on passive membrane properties. The action potentials of circular myometrium of rats up to day 21 of pregnancy were qualitatively similar to those recorded in the same muscle layer from oestrogen-treated, non-pregnant rats and the plateau component was also blocked by relaxin in these tissues. Bursts of spikes were observed in circular strips 24-36 h before parturition, and the effect of the peptide on these was a transient inhibition similar to that observed in longitudinal myometrium. Oxytocin increased the amplitude of the spike and the amplitude and duration of the plateau. Relaxin abolished the plateau in the presence of 10(-11) and 10(-10) M-oxytocin but was ineffective when the concentration of the spasmogen was increased further. Prostaglandin F2 alpha increased the amplitude and duration of the plateau. Relaxin abolished the responses to 10(-10) and 10(-9) M-prostaglandin F2 alpha. The results of this study demonstrate that relaxin specifically inhibits contractions in the circular layer of the myometrium by abolishing the plateau component of the action potential. This action appears to be different from that of other smooth muscle relaxants tested in these experiments (isoprenaline, papaverine and verapamil). All of these abolished simultaneously both the spike and plateau components of the action potential.
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PMID:Relaxin inhibits the plateau component of the action potential in the circular myometrium of the rat. 659 29

In several species the myometrium is quiescent shortly before parturition. At this time high titres of relaxin are present in the plasma and there is evidence that the hormone has a direct inhibitory action on the uterine muscle. Relaxin could also contribute to uterine quiescence by inhibiting oxytocin release. To determine whether relaxin has a central action on the release of oxytocin, we have studied the effect of intravenous injections of porcine relaxin on milk ejection in the anaesthetized lactating rat. We report that reflex milk ejection was suppressed by relaxin in a dose-dependent manner, the onset of inhibition being rapid and lasting from 10 to 60 min. After the period of inhibition the normal temporal pattern of reflex milk ejection was resumed. Mammary sensitivity to exogenous or endogenous oxytocin was reduced by relaxin but not sufficiently to explain the effects observed. Furthermore, relaxin (1 microgram per rat) injected into the cerebral ventricles profoundly disturbed the pattern of reflex milk ejection without affecting the response of the mammary gland to oxytocin. These results suggest a novel role for relaxin within the central nervous system. The site in the brain at which the effects of relaxin are exerted remains unknown.
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PMID:Relaxin affects the central control of oxytocin release. 672 91

Porcine relaxin (30 microgram/ml) when incubated with separated myometrial tissue from 20 day pregnant rats inhibited basal prostacyclin output by 50%. However, relaxin did not inhibit the increased prostacyclin output observed when myometrial tissue was incubated with the prostaglandin precursor, arachidonic acid (10 microgram/ml). When prostacyclin release was stimulated by incubation with oxytocin (10 mU/ml), however, relaxin completely inhibited the increased output. The results suggest that relaxin interferes with basal and oxytocin-stimulated prostacyclin formation in pregnant myometrial tissue by inhibiting the action of the enzyme phospholipase A2 which is responsible for liberating the precursor arachidonic acid endogenously.
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PMID:Relaxin inhibits prostacyclin release by the rat pregnant myometrium. 681 14

Prolactin secretion was stimulated in 5 cyclic gilts during the luteal phase (Day 10-13) with 5 mg haloperidol given i.v. Stimulation of prolactin secretion was also attempted by inducing milk let-down by suckling (4 sows), or by the injection of 1 mg oxytocin i.v. followed by hand milking (3 sows). Plasma prolactin concentrations increased significantly 1-2 h after haloperidol injection, and in 3 of 4 sows during suckling (P = 0.001); plasma relaxin concentrations did not change significantly at these times. No change was observed in plasma prolactin or relaxin concentrations at 15 min or 1-2 h after oxytocin injection and hand milking. Plasma relaxin concentrations ranged from below the sensitivity of the assay (100 pg/ml) to 450 pg/ml in lactating sows and from 100 to 2000 pg/ml in cyclic gilts. The results suggest that in cyclic gilts treated in the luteal phase with a dopaminergic receptor blocker, and in lactating sows during suckling, elevations in plasma prolactin concentrations were not accompanied, during the same period, by detectable changes in relaxin concentrations.
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PMID:Effect of haloperidol, suckling, oxytocin and hand milking on plasma relaxin and prolactin concentrations in cyclic and lactating pigs. 688 39


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