UNIPROT:P01178 - FACTA Search

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

High affinity binding sites for 3[H] oxytocin have been demonstrated in particulate fractions from rat uterus and oviduct, myometrium from the sow, ewe and human, ewe endometrium, and mammary gland from the lactating rat. The binding activity has been localized to enriched plasma membrane fractions from the rat uterus and mammary gland; cells isolated from the mammary gland also bind oxytocin. The apparent dissociation constant (Kd) for the interaction of oxytocin with its binding sites in a variety of tissue preparations is in the nanomolar range. The concentration of oxytocin eliciting half-maximal contraction of the rat isolated uterus corresponds to the apparent Kd of oxytocin interaction with uterine particulate fractions. Binding is specific with respect to the target tissue or cell, as well as to the ligand. The affinity of binding sites for oxytocin analogues corresponds generally to their potencies as agonists or antagonists. Factors that affect the binding of oxytocin affect the biological response in the same way. For example, certain divalent metal ions, which increase oxytocin binding activity, enhance the sensitivity of the contractile response of the uterus and mammary gland to oxytocin. Estrogen administration, which increases the uterine binding of oxytocin, increases the sensitivity of the myometrium to oxytocin. The myometrium binds the most oxytocin at estrus and is most sensitive to oxtocin at that time. The dgree of stimulation by oxytocin of prostaglandin F2alpha synthesis by ewe endometrium is paralleled by an increased concentration of oxytocin binding sites. The marked increase in sensitivity to oxytocin of the rat uterus occurring on the day of parturition also is reflected by the amount of oxytocin bound by the uterus. Because of the many correlations between oxytocin binding and bioactivity, it appears that oxytocin binding sites on the plasma membrane of target cells constitute the recognition part of oxytocin receptors.
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PMID:Characterization of oxytocin receptors in the uterus and mammary gland. 19 1

Renal cell carcinoma has been reported to contain estrogen and progesterone receptors. Thus, it has been suggested that these tumors are hormone dependent in a similar manner described for the breast and prostate cancers. It has been recently shown that mammary and prostate tumor cells contain gonadotropin-releasing hormone (GnRH) receptors and are growth inhibited directly by GnRH antagonists. In this study we examined for the presence of GnRH, estrogen and progesterone receptors in normal and malignant renal tissues. Estrogen receptors were found both in the normal and malignant kidney while progesterone receptors were present only in the normal tissue. Specific binding of [125I]buserelin, a GnRH agonist, was evident in renal carcinoma and in normal kidney and was displaced with equal efficiency by unlabeled buserelin and by D-Trp6-GnRH, but not by unrelated peptides such as thyrotropin releasing hormone and oxytocin. The non-linear scatchard curve obtained for buserelin binding, suggests the presence of at least two binding sites, one with high affinity in the nanomolar range and another in the micromolar range.
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PMID:Gonadotropin-releasing hormone specific binding sites in normal and malignant renal tissue. 133 44

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

We have compared the response of proton and water transport to oxytocin treatment in isolated frog skin and urinary bladder epithelia to provide further insights into the nature of water flow and H+ flux across individual apical and basolateral cell membranes. In isolated spontaneous sodium-transporting frog skin epithelia, lowering the pH of the apical solution from 7.4 to 6.4, 5.5, or 4.5 produced a fall in pHi in principal cells which was completely blocked by amiloride (50 microM), indicating that apical Na+ channels are permeable to protons. When sodium transport was blocked by amiloride, the H+ permeability of the apical membranes of principal cells was negligible but increased dramatically after treatment with antidiuretic hormone (ADH). In the latter condition, lowering the pH of the apical solution caused a voltage-dependent intracellular acidification, accompanied by membrane depolarization, and an increase in membrane conductance and transepithelial current. These effects were inhibited by adding Hg2+ (100 microM) or dicyclohexylcarbodiimide (DCCD, 10(-5) M) to the apical bath. Net titratable H+ flux across frog skin was increased from 30 +/- 8 to 115 +/- 18 neq.h-1.cm-2 (n = 8) after oxytocin treatment (at apical pH 5.5 and serosal pH 7.4) and was completely inhibited by DCCD (10(-5) M). The basolateral membranes of the principal cells in frog skin epithelium were found to be spontaneously permeable to H+ and passive electrogenic H+ transport across this membrane was not affected by oxytocin. Lowering the pH of the basolateral bathing solution (pHb) produced an intracellular acidification and membrane depolarization (and an increase in conductance when the normal dominant K+ conductance of this membrane was abolished by Ba2+ 1 mM). These effects of low pHb were blocked by micromolar concentrations of heavy metals (Zn2+, Ni2+, Co2+, Cd2+, and Hg2+). Lowering pHb in the presence of oxytocin (50 mU/ml) produced a transepithelial current (3 microA.cm-2 at pHb 5.5) which was blocked by 100 microM of Hg2+, Zn2+, or Ni2+ at the basolateral side, and by DCCD (10(-5) M) or Hg2+ (100 microM) from the apical side. The net hydroosmotic water flux (JH2O) induced by oxytocin in frog bladder sacs was blocked by inhibitors of H(+)-adenosine triphosphatase (ATPase). Diethylstilbestrol (DES 10(-5) M), oligomycin (10(-8) M), and DCCD (10(-5) M) prevented JH2O when present in the lumen. These effects cannot be attributed to inhibition of metabolism since cyanide (10(-4) M), or 2-deoxyglucose (10(-3) M) had no effect on JH2O.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Common channels for water and protons at apical and basolateral cell membranes of frog skin and urinary bladder epithelia. Effects of oxytocin, heavy metals, and inhibitors of H(+)-adenosine triphosphatase. 164 38

Estrogen releases into plasma the human oxytocin neurophysin, previously termed the estrogen-stimulated neurophysin. Because oxytocin and its neurophysin are synthesized as part of a common precursor, stimuli which release the hormone should also release neurophysin and vice versa. However, release of oxytocin with its neurophysin has been difficult to demonstrate by immunological assay in humans administered estrogen. Under this condition, the oxytocin immunoreactivity that is released with the oxytocin neurophysin is a novel peptide which is antigenically similar to oxytocin yet is not oxytocin. Co-release of the oxytocin-like peptide with oxytocin neurophysin suggested that the oxytocin-like immunoreactivity may be a partially processed form of oxytocin. To test this hypothesis the synthetic oxytocin precursor intermediates oxytocin-glycine (G), oxytocin-glycine-lysine (GK), and oxytocin-glycine-lysine-arginine (GKR), were tested for cross-reactivity with the various oxytocin antisera used in this laboratory to distinguish the oxytocin-like peptide from oxytocin. Oxytocin-G, but not oxytocin-GK or GKR, showed extensive cross-reactivity with the oxytocin antiserum (Ab 1), which is known to detect the oxytocin-like peptide of human plasma. Plasma from men and rhesus monkeys administered estrogen and from pregnant women was separated by HPLC and oxytocin Ab 1 immunoreactivity was eluted from the column with the same retention time as synthetic oxytocin-G. Estrogen releases an oxytocin precursor intermediate into the circulation of humans and monkeys and may exert an important effect upon posttranslational cleavage of the oxytocin prohormone. These observations suggest a heterogeneity in the intraneuronal posttranslational processing of the oxytocin precursor in estrogen-treated versus nonestrogen-treated primates.
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PMID:An oxytocin precursor intermediate circulates in the plasma of humans and rhesus monkeys administered estrogen. 211 91

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

To test the interaction of various hormones on the myometrium, the following experiments were done studying in vitro contractile activity of uterine segments from immature rats. The rats were divided into two groups: group 1 animals were treated with estrogen (n = 9) and group 2 animals were treated with both estrogen and progesterone (n = 11). Uteri from animals in each group were removed and segments were maintained in a temperature- and pH-controlled organ bath. After baseline contractions were established, uterine segments were treated with either oxytocin and then relaxin, or relaxin and then oxytocin. The dose of relaxin used, 20 ng/ml, was previously shown to be effective in inhibiting uterine contractions of animals treated with either estrogen or estrogen plus progesterone. The dose of oxytocin, 2.5 mlU/ml, was the maximal effective dose shown not to produce prolonged tetany. Estrogen plus progesterone treatment increased the frequency of contractions and resulted in contractions of greater duration of the maximal contractile force, as compared with treatment with estrogen alone. Oxytocin caused a stimulation of contractions in relaxin-inhibited uterine strips. Relaxin decreased the hypertonic contractions produced by oxytocin treatment, resulting in contractions similar to baseline. These data demonstrate that oxytocin and relaxin are directly antagonistic in their effects on uterine contractility. This suggests that labor may occur as a result of increased sensitivity to oxytocin or a decreased sensitivity to relaxin.
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PMID:The antagonistic effect of oxytocin and relaxin on rat uterine segment contractility. 260 21

Estrogen-stimulated neurophysin (ESN) or oxytocin (OT)-neurophysin (Np) was measured in plasma of seven men before and after oral administration of 25 mg diethylstilbestrol (DES). Pre-DES levels of ESN averaged 0.93 +/- 0.3 (+/- SEM) ng/ml and increased to 29.8 +/- 6.5 and 25.4 +/- 5.1 ng/ml 24 and 48 h after DES treatment, respectively. To compare the estrogen-responsive Np in plasma with human OT-Np which is present in the posterior pituitary gland, the Np fraction of post-DES plasma was concentrated by double precipitation with ammonium sulfate and applied to ampholyte displacement and Sephadex G-75 columns. The Np fraction of this plasma extract contained ESN immunoreactivity (IR) but no nicotine-stimulated neurophysin-IR. ESN-IR of plasma and of an extract of human posterior pituitary eluted identically from a Sephadex G-75 column, indicating similar mol wt. The plasma extract containing ESN-IR eluted from the ampholyte displacement column at pH 4.3-4.2. No nicotine-stimulated Np (arginine vasopressin-Np)-IR was found in the plasma samples. ESN-IR in an extract of human posterior pituitary gland eluted from the ampholyte displacement column at the same pH as that of the ESN extracted from plasma. Peak ESN-IR-containing fractions from the ampholyte displacement were pooled, dialyzed, lyophilized, and reconstituted in appropriate carrier buffer for reverse phase high pressure liquid chromatography. The ESN-IR was resolved into two distinct ESN-IR peaks by high pressure liquid chromatography. Plasma and posterior pituitary gave identical pairs of peaks. Thus, the Np that is increased in human plasma in response to estrogen is identical to pituitary OT-Np, providing strong evidence that estrogen stimulates the human neurohypophysis.
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PMID:Ampholyte displacement and high pressure liquid chromatographic separation of the estrogen-responsive neurophysin from human plasma. 374 3

Means of contraception and abortion in cattle are discussed. Estrog en injections (diethylstilbestrol or estradiol benzoate) may be given within a few days of conception, as may oxytocin and prostaglandins. Infusion of a sterile solution into the uterus is another means of inducing abortion. Intrarectal applications of estrogens can also be used to suppress the corpus luteum. Later in pregnancy, injury to the fetus or the membranes, or surgical removal of the fetus are possible. Estrogen or corticosteroid treatment may also be used to induce labor. Because the sperm must be immobilized before they reach the tubes, contraception is difficult to carry out in practice.
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PMID:[Possibilities of contraception, artificial abortion and premature labor in cattle]. 461 33

The effect of oral contraceptives on the neurohypophysis was demonstrated by changes in the plasma level of a posterior pituitary protein. neurophysin. Neurophysins are intraneuronal proteins associated with oxytocin and vasopressin. They have been shown to be released into the bloodstream. The resting plasma level of neurophysin in normal nonpregnant women is 0.69 ng/ml+/-0.7 SD. In women on oral contraceptives, the plasma level is 6.4 ng/ml+/-4.2 SD (P<0.001). Estrogen rather than progesterone causes the elevated neurophysin. The effect is observed within 12-24 h of estrogen administration and disappears 3-11 days after estrogen is discontinued. The results indicate that oral contraceptives act on the neurohypophysis and that estrogen is a potent pharmacologic stimulus useful in studying synthesis and release of neurophysin.
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PMID:Elevation of plasma neurophysin in women on oral contraceptives. 483 90

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