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

The concentration of MSH in serum after estrogen or progesterone injection into gonadectomized rats was measured by a biological assay. Undetectable serum MSH values were found in long-term ovariectomized (OVX) rats. After a single injection of 10 microgram estradiol benzoate (EB) serum MSH exhibited a circadiam rhythm with high levels in the afternoon, while values in the morning were negative. This effect occurred for 4 days following the injection. Progesterone injection into spayed rats also resulted in an increase of serum MSH concentration, but in contrast to the changes observed after EB treatment high values were found in the morning for 3 consecutive days. Afternoon MSH levels were low but measurable. The effect of these steroids on the activity of the hypothalamic enzymes which yielded MIF or MRF upon incubation with oxytocin (OXT) was also studied. Enzymatic activity of both systems was undetectable in OVX rats and was evident after EB treatment. Progesterone increased only the activity of the system which yields MRF. In castrated male rats estrogen elevated baseline MSH levels but a circadian rhythm was not observed, whereas progesterone had no effect. These observations demonstrate a sex difference on steroid-induced MSH release.
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PMID:Effect of estrogen and progesterone on the release of MSH in gonadectomized rats. 2 14

Estradiol, progesterone, prolactin, and 13,14-dihydro-15-keto prostaglandin F2alpha (PGFM) were measured in both maternal and cord venous blood obtained at the time of delivery in 24 maternal infant pairs evenly divided among six different physiologic groups. Progesterone and prolactin were significantly higher and estradiol was significantly lower in cord than in maternal blood. There were no significant differences between the groups for cortisol, estradiol, or progesterone in maternal or cord blood. A significant increase in prolactin was demonstrated in women receiving oxytocin for induction of labor. Both estradiol and PGFM were highly correlated between maternal and cord blood. PGFM was significantly higher in cesarean section patients in labor than in those not in labor in both the maternal and cord circulations. Among those delivered vaginally, PGFM tended to be higher in those in spontaneous labor than in those with induced labor. PGFM in induced labor was intermediate between spontaneous labor aptients delivered by cesarean section and those delivered vaginally. Duration of labor was negatively correlated with cord estradiol concentration. The physiologic significance of these findings is discussed.
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PMID:Interrelationships between maternal and cord prolactin, progesterone, estradiol, 13,14-dihydro-15-keto-prostaglandin F2alpha, and cord cortisol at delivery with respect to initiation of parturition. 56 75

Intrauterine pressure was monitored in vivo in oestrogen-treated ovariectomized ewes before, during and after treatment with progesterone (50 mg s.c./day for 3 days). Progesterone reversibly reduced the frequency and amplitude of myometrial activity and abolished uterine reactivity to oxytocin (i.v.) and PGF-2alpha (intrauterine infusion). The rate of rise of intrauterine pressure during active pressure cycles was significantly reduced. These results confirm that the action of progesterone on the ovine myometrium is comparable to the classic progesterone 'block'. The intrauterine infusion of PGF-2alpha (10 microgram/min), which elicited a marked mechanical response in the control animals, failed to stimulate the progesterone-'blocked' uterus, suggesting that the inhibition produced by progesterone is due to a direct action of the hormone on the uterine muscle and not to an indirect mechanism operating through endometrial prostaglandin output.
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PMID:Demonstration that progesterone 'blocks' uterine activity in the ewe in vivo by a direct action on the myometrium. 62 2

The changes in unconjugated estradiol-17beta and estriol, progesterone and chorionic somatomammotropin (HCS) in peripheral plasma have been studied in 18 women at 30-minute intervals following intra-uterine prostaglandin E2 administration for therapeutic termination of second trimester pregnancy. The hormonal changes were related to the time of fetal death detected by the disappearance of fetal heart pulsations. Prostaglandin E2 was given by the intra-amniotic route with urea (5 patients) or with intravenous oxytocin (5 patients), or by the extra-amniotic route with intravenous oxytocin (8 patients). Fetal death occurred rapidly with intra-amniotic PGE2, but usually at a late stage with extra-amniotic PGE2. Three fetuses in the extra-amniotic group died at or just before abortion. A variety of fetal heart changes were noted and the time of fetal death did not appear to influence the time of abortion within each treatment subgroup. Estradiol and estriol showed a sligh but persistent fall over 24 hours prior to induction of abortion. A more rapid fall usually occurred after induction, with a consistent fall around the time of fetal death. Progesterone and HCS usually fell much less before and immediately after fetal death. A marked rise in estradiol sometimes occurred before fetal death, particularly in the intraamniotic PGE2 and urea subgroup. Estriol levels declined more rapidly before than after fetal death, whereas fetal death had less consistent effects on the other hormones. All hormones had usually fallen considerably at the time of abortion, and in some individuals marked fluctuations in hormone levels were seen.
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PMID:Hormone changes in relation to the time of fetal death after prostaglandin-induced abortion. 88 4

The interaction between oestrogen and progesterone in the regulation of the uterine oxytocin receptor in sheep was evaluated by measuring the binding of oxytocin to membrane preparations of caruncular and intercaruncular endometrium and myometrium. Ovariectomized ewes were assigned in groups of five to each cell of a 4 x 2 factorial design. The four treatments were (a) vehicle (maize oil) for 12 days, (b) progesterone (10 mg day-1) for 9 days, (c) progesterone for 9 days followed by maize oil until day 12 and (d) progesterone for 12 days. The two oestradiol treatments consisted of the administration of implants in the presence or absence of oestradiol. The ewes were killed on day 10 (group b) or day 13 (groups a, c and d) for collection of uterine tissues. The response of the caruncular and intercaruncular endometrium to the treatments was similar. In the absence of oestradiol, treatment with progesterone continuously for either 9 or 12 days reduced the concentration of the oxytocin receptor in comparison with both the control and the progesterone withdrawal group (in which values were similar). The presence of oestradiol reduced the receptor concentrations in control and both 9- and 12-day continuous progesterone treatment groups, but enhanced the concentration in the progesterone withdrawal group. The myometrial oxytocin receptors responded in a similar way to those in the endometrium to progesterone treatment alone, but the addition of oestradiol produced no further effect. In conclusion, progesterone and oestradiol caused downregulation of the endometrial oxytocin receptor. On the other hand, progesterone withdrawal, similar to that which occurs during luteolysis, increased receptor density in the presence of oestradiol. Progesterone may influence the response of the myometrium to oxytocin by causing a reduction in receptor density.
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PMID:Role of progesterone and oestradiol in the regulation of uterine oxytocin receptors in ewes. 131 47

The facilitation of sexual receptivity by oxytocin (OT) in female rats is related to the regulation of oxytocin receptors (OTR) by ovarian steroids in the ventromedial nuclei (VMN) of the hypothalamus. In a previous study, we have shown that estradiol benzoate (EB) causes a twofold increase in OTR binding in the VMN. Progesterone (P) then modulates levels of the estrogen-induced OTR and increases the area occupied by the receptors by acting on the neuronal membrane. In the present study, we compared the effects of EB and P on OTR binding between males and females. In both sexes, EB increased the density of OTR and the area covered by the receptors at the level of the medial and caudal VMN. In estrogen-primed females, P further increased OTR levels in the medial VMN and the area covered by OTR at the level of the caudal VMN. By contrast, P did not modulate OTR binding in estrogen-primed males. Thus, the behavioral insensitivity of male rats to ovarian hormones, in particular to P, may be related to sex differences affecting the modulation of OTR binding.
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PMID:Sex differences in the regulation of oxytocin receptors by ovarian steroids in the ventromedial hypothalamus of the rat. 132

This literature review, which describes the structure of myometrial muscle and the regulation of its contractility, cites research from 1971 to 1989. The functions of the myometrium and the cervix are interrelated and coordinated during pregnancy and labor. The structure of smooth muscle, by allowing contraction in any direction, permits the uterus to assume the shape and size necessary to accommodate the fetus. Myometrial smooth muscle cells communicate via gap junctions, which synchronize myometrial function via conduction of electrophysiological stimuli during labor. These junctions increase in number prior to labor. This is regulated by estrogen, progesterone, and prostaglandins (PGs). The structures of myosin and actin and their movement during contraction are described. Estrogen, via alpha adrenergic receptors, causes a decrease in cAMP levels. It also increases the number of oxytocin receptors. Progesterone, via beta adrenergic receptors, causes an increase in cAMP levels. While estrogen leads to increased production of PGF2alpha, progesterone stimulates the production of prostacyclin synthase, Mifepristone, which blocks progesterone at the receptor level, increases uterine activity and sensitivity to PG. Human amnion and chorion produce mainly PGE2. The decidua produces PGE2 and PGF2alpha. Prostaglandins induce uterine activity at all stages of gestation when they are administered exogenously. Their production by uterine tissues increases during pregnancy, as does their concentration in amniotic fluid and in maternal blood and urine. Their roles in labor, whether natural or induced, include the softening of the cervix, the induction of gap junctions, and the direct stimulation of myometrial contractions. Although PGE2 and PGF2alpha relax cervical smooth muscle, they contract the myometrium by acting as calcium ionophpores. The production of PGE2, PGF2alpha, and other eicosanoids by the fetoplacental production of PGE2, PGF2alpha, and other eicosanoids by the fetoplacental unit is related to increased contractile activity during labor. What is produced in the eiconsanoid pathway changes dynamically with the phases of the reproductive cycle and the local concentrations of enzymes. Because of the rise in arachidonic acid in amniotic fluid during labor, fetal membranes may be involved with the initiation of regular uterine contractions. In addition, any stimulus facilitating PGE2 synthesis in the fetal membrane (hypoxia, infection, exposure to oxytocin, hypertonic solutions, prostaglandins, or arachidonic acid) would induce the same series of steps leading to formation of PGF2alpha in the decidua and the myometrium. Since natural prostaglandins are rapidly metabolized, and induction of abortion requires a longer presence, analogues have been developed for this use. These include gemeprost, sulprostone, and minprostin. Their action is more prolonged and specific to uterine tissue than their parent compounds.
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PMID:Biochemistry of myometrial contractility. 133 53

Intact cyclic ewes have been used in experiments designed to examine the mechanism by which uterine oxytocin receptor synthesis is controlled during the oestrous cyclic. Previous experiments have shown that the prostaglandin F2 alpha analogue cloprostenol is luteolytic in ewes receiving oxytocin by continuous intra-venous infusion. When ewes receiving oxytocin are given cloprostenol uterine oxytocin receptor concentrations are raised, whereas in animals receiving oxytocin alone, they remain low. To investigate whether inhibition of oxytocin receptor binding activity by oxytocin is either dependent on elevated plasma progesterone concentrations or over-ridden by oestrogens secreted by ovarian follicles maturing as a result of cloprostenol treatment, ewes were given oxytocin by continuous intravenous infusion (3 nmol h-1) between Days 12 and 17 after oestrus and one of the following: no further treatment; cloprostenol [125 micrograms intramuscularly (i.m.)] on Day 15; progesterone, by subcutaneous implant, from Day 14 with cloprostenol on Day 15; medroxyprogesterone acetate (MPA; 6 mg depot i.m.) on Day 14 followed by cloprostenol on Day 15; or oestradiol-17 beta (2.75 mumol i.m.) on Days 14 and 15. Concentrations of oxytocin receptor were measured at autopsy on Day 17 in caruncular endometrium, intercaruncular endometrium and myometrium. Ovarian follicles and corpora lutea were examined to determine the effect of treatment on these tissues. Treatment with oxytocin alone resulted in the maintenance of corpora lutea, reduced follicular development and a low concentration of uterine oxytocin receptor. Cloprostenol initiated luteolysis in oxytocin-treated ewes. This was associated with a high level of oxytocin receptor binding activity in all ewes except those receiving exogenous progesterone.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of continuous infusion of oxytocin on ovarian function and uterine oxytocin receptor concentration in the cyclic ewe. 133 7

In the present paper the effects of nonapeptide hormones and of some of their chemical analogues were investigated on progesterone and testosterone production in granulosa cells of sow ovaries; the experiments were made in vitro. This objective was given by data on potential regulatory roles of nonapeptides at the level of hypothalamus, pituitary and reproductive organs. The goal of this experiment was to analyze the effects of various doses of oxytocin (OT), arginine-8-vasopressin (AVP), arginine-8-vasotocin and of some of their analogues on progesterone and testosterone production in vitro in granulosa cells of sow ovaries. The production activity of granulosa cells was investigated which were obtained from slaughtered sows without any changes in their reproductive process and abnormalities in their reproductive organs. Follicles of the size 2-5 mm without marked paleness in the early follicular phase were selected for aspiration. Granulosa cells with determined viability (more than 75%) and concentration (2 million/ml) were cultivated in defined culture conditions (37.5 degrees C, 5% CO2) after threefold resuspension and centrifugation of follicle fluid. These hormonal preparations were used in the experiments: pFSH, synthetic OT, synthetic AVP, synthetic AVP with antidiuretic effects and synthetic AVT. Progesterone and testosterone concentrations were analyzed radioimmunoanalytically using commercial kits of the Institute of Radio ecology and Nuclear Technology at Kosice. Statistically significant differences between the groups were evaluated by Student's t-test. The administered preparations were found to influence progesterone and testosterone production in dependence on the doses applied (Figs. 1-6). OT stimulation of progesterone production in granulosa cells indicated its regulatory role in relation to secretion of this hormone.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Production of progesterone and testosterone in ovarian granulosa cells in sows after administration of nonapeptide hormones in vitro]. 141 99

Changes in the ability of the uterus to secrete prostaglandin F2 alpha (PGF2 alpha) in response to oxytocin may play a critical role in determining when endogenous secretion of PGF2 alpha begins. The cellular mechanisms that regulate uterine secretion of PGF2 alpha in response to oxytocin have not been completely defined. Several intracellular components that may contribute to this regulation have been studied, including phospholipase C (PLC), prostaglandin H endoperoxide synthase (PGS) and receptors for oxytocin. All of these components change during the oestrous cycle and are associated with the development of uterine secretory responsiveness to oxytocin. Progesterone appears to play the principal role in regulating oxytocin receptors, PLC and PGS. The conceptus appears to suppress the increase in receptors for oxytocin and PLC activity that typically occurs around the time of luteal regression.
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PMID:Uterine secretion of prostaglandin F2 alpha in the ewe: regulation at the cellular level by ovarian hormones and the conceptus. 143 63


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