Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Estradiol-17beta administration to young (10- to 12-week-old) rabbits to produce the "estrogen-dominated" uterus increased the uterine contractile response to both oxytocin and methacholine in vitro. In "progesterone-dominated" uteri, obtained from rabbits that received progesterone for 4 days after estrogen pretreatment, the contractile response to oxytocin in vitro was selectively abolished; the response to methacholine was unaffected. Parallel changes were observed in the concentration (but not affinity) of specific sites in uterine microsomal membranes that bind [(3)H]oxytocin with selectivity features expected for oxytocin receptors. Thus, estrogen-dominated uteri have an increased number of specific [(3)H]oxytocin binding sites per mg of membrane protein relative to untreated controls, whereas specific oxytocin binding sites are reduced to barely detectable levels in the progesterone-dominated uterus. Similar results are obtained when binding sites are measured in membranes from the myometrium of estrogen- or progesterone-dominated uteri. Short-term (24-hr) progesterone administration to estrogen-pretreated rabbits decreased, but did not abolish, specific [(3)H]oxytocin binding; the concentration of specific [(3)H]oxytocin binding sites was reduced without influence on the affinity of these sites. A sublethal dose of actinomycin D, administered over a 24-hr period to rabbits pretreated with estradiol for 4 days, likewise reduced specific oxytocin binding; additive effects were not observed when progesterone and actinomycin D were administered together. These results suggest that the regulatory effects of estrogens and progesterone upon the rabbit uterine contractile response to oxytocin are achieved, at least in part, by the opposing actions of these steroids in regulating the number of oxytocin receptors in smooth muscle cells. Estradiol increased the concentration of uterine oxytocin receptors; the maintenance of high receptor levels appears to depend upon the continuous de novo synthesis of oxytocin receptors. In contrast, progesterone, like actinomycin D, appears to act at the nuclear locus to repress synthesis of oxytocin receptors.
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PMID:Opposing effects of estradiol and progesterone on oxytocin receptors in rabbit uterus. 20 80

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

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

Oxytocin (OT) neurotransmission in the brain has a facilitatory effect on sexual receptivity in rats. This effect of OT is dependent on priming by ovarian steroids, estrogen and progesterone. These steroids modulate OT binding in specific brain nuclei, including the ventrolateral portion of the ventromedial hypothalamic nucleus (vlVMN). In the present study, single-unit activity was recorded from the vlVMN in hypothalamic slices to characterize the electrophysiological actions of OT. To examine the effects of ovarian steroids on OT actions, we used brain slices prepared from ovariectomized rats either treated with estrogen or not, and some slices were treated with progesterone in vitro. OT had little modulatory action on neuronal responses to other agents, but affected the activity of large numbers of vlVMN units. Of those neurons affected, 94% responded with excitation. This predominant stimulatory action of OT is consistent with its lordosis-facilitating effect, because increases in the activity of VMN neurons are generally associated with the facilitation of lordosis. Pharmacological analyses with selective OT agonists and antagonists as well as structurally related peptides showed that the excitatory action of OT is mediated by OT receptors. Estradiol modulated several aspects of OT transmission. First, it increased neuronal responsiveness to OT, especially at the lowest concentration used (0.2 nM). In addition, it caused neuronal responses to OT to correlate significantly with responses to acetylcholine and norepinephrine, which also can act on the ventromedial hypothalamus to facilitate lordosis. Finally, estradiol enhanced the excitability of laterally projecting neurons, which have been implicated in lordosis. In estrogen-pretreated slices, addition of progesterone in vitro caused little further effect on responses of individual neurons to exogenous OT. Altogether, the present electrophysiological findings are consistent with the hypothesis that estrogen potentiates OT action by increasing functional OT receptors preferentially in lordosis-relevant neurons, thereby enabling OT to efficiently facilitate female reproductive behavior.
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PMID:Electrophysiological actions of oxytocin on hypothalamic neurons in vitro: neuropharmacological characterization and effects of ovarian steroids. 174 64

Progesterone and estradiol interact to regulate secretion of prostaglandin (PG) F2 alpha from the ovine endometrium in response to oxytocin. Two experiments were conducted to determine if these effects were due to changes in activity of phospholipase C or in the second messenger responsive pathways that regulate production of PGF2 alpha. In both experiments, ovariectomized ewes were assigned to one of four treatment groups (control, estradiol, progesterone, progesterone and estradiol). Steroids were administered, in vivo, to mimic the changes that occur during the estrous cycle. On Day 16 of steroid treatment, endometrial tissue was collected and incubated, in vitro, to measure activity of phospholipase C and release of PGF2 alpha. Treatment with progesterone, in vivo, enhanced basal and oxytocin-induced activity of phospholipase C and release of PGF2 alpha, in vitro. Estradiol suppressed oxytocin-induced activity of phospholipase C, both in the presence and absence of progesterone. In contrast to its effects on phospholipase C, estradiol inhibited basal and oxytocin-induced release of PGF2 alpha when administered alone, but not when administered with progesterone. Steroids had similar effects on the release of PGF2 alpha induced by phorbol 12-myristate 13-acetate and A23187. It was concluded that progesterone and estradiol regulate endometrial release of PGF2 alpha by affecting both the activity of phospholipase C and its associated second messenger responsive pathways that may regulate production of PGF2 alpha.
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PMID:Activity of phospholipase C and release of prostaglandin F2 alpha by endometrial tissue from ovariectomized ewes receiving progesterone and estradiol. 201 59

Distal (D) segments of the pregnant rat uterine horn express myometrial oxytocin receptors (MORs) earlier than proximal (P) segments (day 18 vs. 20, respectively); the levels in D segments remain higher than in P segments throughout days 21-22 and correlate with the segment-specific myometrial sensitivity to oxytocin. While progesterone (P4) had no effect on MOR levels, RU486 increased (t1/2 6-12 h) MOR levels both in D and P segments, particularly in days 12-17, and the levels in the P segment equaled those in the D segment. Estradiol had no effect on MOR levels in days 20-22; in days 16-19 estradiol increased MOR levels particularly in the P segment, and the levels in the latter were higher than in the D segment. Capillary plasma P4 levels were higher in P vs. in D myometrial segments. These results indicate, in the pregnant rat, a local uterine control of D greater than P MOR expression by P4 withdrawal beginning in day 18. We hypothesize that the D greater than P MOR expression determines a role for oxytocin in initiating myometrial contractions in the D segment, while in active labor another class of agent(s) assume that function in more proximal segments.
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PMID:Myometrial oxytocin receptors levels in the pregnant rat are higher in distal than in proximal portions of the horn and correlate with disparate oxytocin responsive myometrial contractility in these segments. 216 6

The ventromedial nuclei of the hypothalamus (VMN) are important for the control of feminine mating behavior, and hormone action within these nuclei has been causally related to behavior. Estradiol induces receptors for oxytocin in the VMN and in the area lateral to these nuclei over the course of 1 to 2 days, and progesterone causes, within 30 minutes of its application, a further increase in receptor binding and an expansion of the area covered by these receptors lateral to the VMN. The rapid progesterone effect appears to be a direct and specific effect of this steroid on the receptor or membrane, because it was produced in vitro as well as in vivo and was not mimicked by a variety of other steroids. The effect of progesterone occurred in the posterior part of the VMN, where oxytocin infusion facilitated feminine mating behavior; it did not take place in the anterior part of the VMN, where oxytocin infusion had no effect on mating behavior.
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PMID:Behavioral effects of progesterone associated with rapid modulation of oxytocin receptors. 217 39

Estrogen receptors are distributed in discrete areas of the hypothalamus, preoptic area and amygdala of the rat brain, and in some of these areas estrogens induce progestin receptor sites. Estradiol (E), followed by progesterone (P), induce feminine sexual behavior in female, but not in male, rats. This induction takes time (on the order of hours, not minutes, so that the hormone may be cleared from the body) and is dependent on RNA and protein synthesis. Within the hypothalamic ventromedial nuclei (VMN), E and P induce changes in RNA and protein synthesis and also induce morphological changes indicative of cellular growth, genomic activation, and either new synapse formation or morphological rearrangement of existing synapses. Neurochemically, a number of neurotransmitter systems are implicated in the control of feminine sexual behavior, including acetylcholine, serotonin, GABA, and the neuropeptides, oxytocin and CCK. One of the means by which E and P may exert their influence on sexual behavior, aside from the morphological alterations, is by regulating levels of receptors for certain of these neurotransmitters. The critical differences which underlie the inability of male rats to display high levels of feminine sexual behavior after E plus P priming may depend on sex differences in the ability of E to induce particular neurochemical products as well as P receptors and upon differences in neural circuitry in the VMN.
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PMID:Genomic regulation of sexual behavior. 245 98

Two ovarian hormones, estradiol and progesterone, which facilitate mating behavior in the female rat by acting on the ventromedial nuclei (VMN) of the hypothalamus, induce changes in oxytocin receptor binding in this brain region. Estradiol induced a 4-fold increase in the oxytocin receptor binding of the VMN and surrounding area and increased the number and immunostaining of oxytocin fibers in an area lateral to the ventral VMN. Progesterone, in estrogen-primed rats, caused the induced oxytocin receptors to spread over the area containing the oxytocin fibers. Infusion of oxytocin into the ventromedial hypothalamus increased the display of lordosis behavior only in females primed with both estradiol benzoate and progesterone. Thus, the sequential actions of two ovarian hormones bring a neuropeptide and its receptors into register and enable the neuropeptide to exert behavioral effects.
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PMID:Localized actions of progesterone in hypothalamus involve oxytocin. 254 47

Electromyographic (EMG) recordings were made during the last two weeks of pregnancy from two mares. Four bipolar EMG electrodes were implanted in the uteri of the mares; near the tubo-uterine junction and bifurcation of the pregnant horn, in the body of the uterus and near the cervix. Plasma samples were collected every 4 hours during the same period and more intensely during parturition. Estradiol 17 beta, progesterone, PGF2 alpha metabolite and oxytocin were measured by radioimmunoassay. During the last week preceding delivery, EMG activity was elevated and was greatest at night. EMG activity was further increased during the last 24 hours before delivery of the foal and reached its highest intensity for 7 to 13 hours immediately prepartum. This period of intense activity is described as stage I of parturition. EMG activity decreased to very low levels 2 to 4 hours before delivery but abruptly increased again at rupture of the choriollantois and continued through delivery when activity decreased again until delivery of the placenta. The ratio of estradiol 17 beta to progesterone (E 17 beta/P) increased through the last week prepartum due to an increase in the level of estradiol 17 beta concentrations and during the last 24 hours the change in the E 17 beta/P ratio was due to a significant decrease in progesterone. Oxytocin and PGF2 alpha metabolite increased abruptly just before rupture of the fetal membranes and there is some evidence that oxytocin increased prior to PGF2 alpha metabolite. We hypothesize that the increasing E 17 beta/P ratio allows the evolution of labor to occur during the daylight hours preceding parturition.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Pregnancy and labor in the mare: uterine activity and endocrinology]. 271 55


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