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)

The plasma antidiuretic hormone (ADH) concentration and the kidney medulla responsiveness to vasopressin were measured in adult jerboas ( Jaculus orientalis) in different states of hydration. In 15 jerboas adapted to 30 degrees and fed a dry diet, the average ADH concentration in blood plasma was 479 +/- 59 pg/ml, as measured by a radioimmunoassay. About 6 hr after receiving a 5% body wt water load by gavage, the plasma ADH concentration fell to 130 +/- 30 pg/ml in the 5 jerboas still producing hypertonic urine (1022 +/- 267 mosmol/liter) and to 41.5 +/- 8.4 pg/ml in the 6 jerboas producing hypoosmotic urine (157 +/- 6 mosmol/liter). In vitro biochemical experiments were performed on the kidney medullas from two groups of 5 jerboas fed a dry diet (group I) or a water-enriched diet (group II), respectively, for 4 to 7 weeks. Compared to group II, group I animals exhibited (a) higher plasma ADH values, 372 +/- 86 versus 76 +/- 25 pg/ml; (b) higher urine osmolarities (3817 +/- 638 versus 647 +/- 90 mosmol/liter); (c) some decrease in [3H]lysine-vasopressin (LVP) binding capacity to kidney membrane fractions (maximal binding: 0.4 versus 0.6 pmol [3H]LVP bound/mg protein); d) decreased adenylate cyclase responses to arginine-vasopressin, lysine-vasopressin, and oxytocin in kidney membrane fractions; and (e) weaker adenylate cyclase responses to arginine-vasopressin in microdissected pieces of the medullary thick ascending limb of Henle's loop. The values found for (a) the dissociation constant of [3H]lysine-vasopressin binding to membranes (KD); (b) adenylate cyclase sensitivity to the three neurohypophyseal hormones (KA); and (c) adenylate cyclase sensitivity to arginine-vasopressin (KA) in medullary collecting tubules and medullary thick ascending limbs are similar in the two groups of jerboas and roughly comparable to those previously reported for the rat kidney medulla. The reduced maximal adenylate cyclase responses to vasopressin in the jerboas fed a dry diet might indicate some physiological "down regulation" of the number of vasopressin-specific receptors in the kidney as a result of the huge ADH concentration present in blood plasma under these conditions. However, this desensitization is not sufficient to account for the production of hypoosmotic urine in spite of the relatively high ADH plasma levels which persisted after acute overhydration.
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PMID:Plasma antidiuretic hormone levels and kidney responsiveness to vasopressin in the jerboa, Jaculus orientalis. 673 46

The mechanism for the luteolytic release of prostaglandin (PG)F2 alpha in swine is not known. This study examined the potential role of oxytocin (OT)-induced phosphoinositide (PI) hydrolysis in promoting PGF2 alpha secretion in vitro from the endometrium of cyclic gilts on Day 15 postestrus. In Experiment 1, endometrial PI hydrolysis was increased (P < 0.05) by 100 nM OT and was increased quadratically (P < 0.05) by LiCl, but was not affected by the LiCl x OT interaction (P > 0.30). PI hydrolysis was maximal at 50 mM LiCl and declined at 100 mM LiCl. In Experiment 2, endometrial PI hydrolysis and PGF2 alpha secretion were similarly increased (P < 0.01) by 0, 0.1, 1, 10, and 100 nM OT in a dose-dependent manner. In Experiment 3, the linear increase in PI hydrolysis occurring 0, 3, 5, 10, and 20 min after treatment was greater (P = 0.01) for tissue treated with 100 nM OT than for the tissue treated with 0 nM OT. The quadratic increase (P < 0.05) in PGF2 alpha secretion occurring 0, 3, 5, 10, and 20 min after treatment was greater (P < 0.05) for tissue treated with 100 nM OT than for the tissue treated with 0 nM OT. In Experiment 4, AlF4- (an activator of Gp and phospholipase C) similarly increased (P < 0.01) PI hydrolysis and PGF2 alpha secretion. In Experiment 5, PI hydrolysis (P < 0.01) and PGF2 alpha secretion (P < 0.05) were increased by 100 nM OT but were not stimulated by cholera toxin (an activator of Gs and adenylate cyclase). Cholera toxin also did not enhance PI hydrolysis and PGF2 alpha secretion in response to 0.1 or 100 nM OT. These results are consistent with the hypothesis that OT may induce PI hydrolysis to stimulate the endometrial secretion of PGF2 alpha during corpus luteum regression in swine.
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PMID:Relationship between phosphoinositide hydrolysis and prostaglandin F2 alpha secretion in vitro from endometrium of cyclic pigs on day 15 postestrus. 762 82

Previous work demonstrated that human fat-cells possess a plasma-membrane-bound H2O2-generating system that is activated by insulin. Here we show that this system is under antagonistic control by various hormones and cytokines that typically act through several distinct receptor families. Similarly to insulin, oxytocin and tumour necrosis factor alpha acted as stimulators of NADPH-dependent H2O2 generation, whereas isoprenaline, a beta-adrenergic agonist, had inhibitory effects. Surprisingly, the acidic and basic isoforms of fibroblast growth factor as well as homodimeric platelet-derived growth factor AA and BB had antagonistic stimulatory and inhibitory effects on NADPH-dependent H2O2 generation. The agents tested acted at discrete ligand-specific receptors and their mechanisms of action were membrane-delimited and occurred in the absence of ATP. These findings implied that established pathways of signal transduction, including receptor kinases or second-messenger-dependent protein kinases A and C, were not involved and placed the stimulus-sensitive H2O2-generating system in a position comparable with adenylate cyclase. It was concluded that the stimulus-sensitive H2O2-generating system of human fat-cells meets all criteria of a universal signal-transducing system for hormones and cytokines that may link ligand binding to cell-surface receptors to changes in the intracellular redox equilibrium.
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PMID:The stimulus-sensitive H2O2-generating system present in human fat-cell plasma membranes is multireceptor-linked and under antagonistic control by hormones and cytokines. 773 95

Cytosolic free calcium concentration ([Ca2+]i) was measured in single microdissected rat medullary collecting tubules [outer (OMCD) and inner (IMCD)] to identify receptors involved in vasopressin (AVP)-induced [Ca2+]i increases. In both segments, [Phe2,Orn8]vasotocin ([Phe2,Orn8]VT), a specific V1 agonist, as well as the V2 agonist 1-desamino-8-D-AVP (dDAVP) triggered [Ca2+]i variations. In OMCD, the mean response to 10 nM AVP roughly corresponded to the sum of V1 and V2 agonists effects. In IMCD, dDAVP (10 nM) alone reproduced the calcium response to AVP (delta[Ca2+]i = 243 +/- 34 nM, n = 6, and 248 +/- 27 nM, n = 8, with dDAVP and AVP, respectively). Furthermore, in the same experiments V1 and V2 maximal effects were not additive ([Phe2,Orn8]VT = 154 +/- 21 nM, n = 6; dDAVP + [Phe2,Orn8]VT = 233 +/- 23 nM, n = 9). As AVP, dDAVP released intracellular calcium (delta[Ca2+]i in calcium-free medium = 182 +/- 24 nM, n = 8, vs. 182 +/- 14 nM, n = 6 with 10 nM dDAVP and AVP, respectively). Neither 8-(4-chlorophenyl-thio)-adenosine 3',5'-cyclic monophosphate nor forskolin modified [Ca2+]i. A cross-reaction of dDAVP with an oxytocin (OT) receptor can be excluded since 1) the specific OT agonist [Thr4,Gly7]OT (10 nM) increased only slightly [Ca2+]i (delta-[Ca2+]i = 20 +/- 5 nM, n = 11); 2) the dDAVP response was not altered by the specific OT antagonist [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid),2-(O-methyl)tyrosine,4-threonine, 8-ornithine,9-tyrosylamide]vasotocin [d(CH2)5(1),O-Me-Tyr2,Thr4,Tyr-NH2(9)]OVT; 3) it was insensitive to V1 antagonists but was totally blocked by the V1/V2 antagonist [d(CH2)5(1),O-Et-Tyr2,Val4]AVP ([delta[Ca2+]i = 18 +/- 4 nM, n = 6). These results indicate that in IMCD AVP increases [Ca2+]i via both V1 and V2 receptors. [Ca2+]i variations due to V2 receptors involve a mechanism independent of adenylate cyclase and coupled to the same intracellular calcium pool as V1 and V2 receptors.
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PMID:V2-like vasopressin receptor mobilizes intracellular Ca2+ in rat medullary collecting tubules. 834 13

Prostaglandin (PG) production by human amnion has been postulated to have a role in the onset of labor. Previous work by ourselves and others has demonstrated that oxytocin, phorbol esters and epidermal growth factor (EGF) increase PGE2 production in human amnion cells by activation of the Phospholipase C/Protein Kinase C (PKC) cascade system. The present study was undertaken to determine the effect of prior activation of the Adenylate Cyclase cascade system upon subsequent stimulation of PGE2 production by oxytocin, phorbol 12-myristate-13-acetate (PMA) or EGF in amnion cells and membrane discs. Isoproterenol, forskolin and dibutyryl cyclic adenosine monophosphate (dbcAMP) were utilized to activate the Adenylate Cyclase system at the receptor, enzyme and second messenger level. In control amnion cells, oxytocin, PMA and EGF each provoked dose dependent increases in PGE2 production. In cells preincubated with dbcAMP, forskolin or isoproterenol, agonist stimulated PGE2 production was markedly (50-90%) inhibited (p < 0.01). Inhibition was dose dependent upon preincubator concentrations. Maximal inhibition by adenylate cyclase activators occurred with 2-4 h of preincubation. In membrane discs, forskolin preincubation also inhibited oxytocin, PMA and EGF stimulation of PGE2 production. Activation of the Adenylate Cyclase system in human amnion cells or membrane discs inhibits the subsequent action of potent stimulators of PGE2 production in human amnion.
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PMID:Protein kinase A activators inhibit agonist induced prostaglandin production in human amnion. 839 7

[Arg8]vasopressin and oxytocin are the two main members of the neurohypophysial hormone family found to be present in nearly all mammals. [Lys8]vasopressin ([Lys8]VP) has been identified as the antidiuretic hormone in pig and some marsupial families. The porcine-derived kidney epithelial cell line, LLC-PK1, expresses both [Lys8]VP receptors coupled to the activation of adenylate cyclase (V2 receptors) and oxytocin receptors. Here we report the molecular cloning of the V2 [Lys8]VP receptor and the oxytocin receptor from LLC-PK1 cells. The cloned V2 [Lys8]VP receptor differs from human and rat V2 [Arg8] receptors mainly in its N-terminal region, in residues located in the extracellular loops and in intracellular phosphorylation sites. When expressed in COS7 cells, the V2 [Lys8]VP receptor exhibits the relative order of ligand affinity [Lys8]VP = [Arg8]VP >> 1-deamino[D-Arg8]VP > or = oxytocin and adenylate-cyclase stimulation, expected for the porcine V2 [Lys8]VP receptor but different from V2 [Arg8]VP receptors. Adenylate-cyclase activation by [Lys8]VP was inhibited in COS7 cells by a V2 antagonist. The cloned oxytocin receptor exhibits in COS7 cells a ligand specificity typical of mammalian oxytocin receptors. mRNA-distribution analysis revealed a single 5.5-kb transcript in the uterus from pregnant guinea pig.
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PMID:Molecular cloning and functional characterization of V2 [8-lysine] vasopressin and oxytocin receptors from a pig kidney cell line. 839 86

1. Immunocytochemically identified magnocellular neurosecretory cells (MNCs) in the guinea-pig supraoptic nucleus (SON) were studied using the in vitro intracellular recording technique. Cells were identified as containing arginine vasopressin (AVP) or oxytocin (OT) following recordings made with biocytin-filled electrodes. Both AVP and OT MNCs demonstrated a fusiform or pyramidal shape (15-20 microns by 26-39 microns), with two to three processes. There were no significant differences in the proportion of AVP and OT cells in the retrochiasmatic (caudal) versus the rostral slices. 2. No significant differences in passive membrane properties were observed between AVP and OT cells, except that AVP cells exhibited a significantly broader action potential width (1.51 +/- 0.1 ms, n = 11) than did OT cells (1.01 +/- 0.08 ms, n = 7). 3. Firing patterns were recorded for 100 MNCs, 41% of which fired in a phasic manner (repeated clustering of action potentials into bursts). Of the seventy-seven cells which were immunocytochemically identified, only AVP-containing MNCs displayed phasic firing. Phasic firing occurred only in MNCs demonstrating a depolarizing potential which followed hyperpolarizing after-potentials (HAPs). The presence of the depolarizing potential was not always associated with phasic firing, however, as both OT cells and non-phasic AVP cells sometimes exhibited a depolarizing potential. 4. In 160 MNCs examined for the presence of the time-dependent inward rectification (TDR in current clamp, or Ih in voltage clamp), a significant difference in the proportion of cells expressing the Ih was observed in the two cell types. The Ih was expressed in forty-five of fifty-four AVP MNCs (83%) and in six of fifteen OT MNCs (40%). No significant association was found with firing pattern. 5. The Ih exhibited properties similar to those found in other CNS and peripheral tissues. It appeared on steps to potentials more hyperpolarized than -65 mV. It was augmented by raising the extracellular potassium concentration, blocked by 2 mM CsCl, and insensitive to 100-500 microM BaCl2. Activation followed a single exponential, and the time constant of activation was voltage dependent. 6. The adenylate cyclase activator forskolin increased the Ih and shifted its activation curve to more depolarized levels. In cells recorded for several hours, the Ih varied in amplitude, suggesting intrinsic modulation, possibly by intracellular second messenger systems. The Ih in guinea-pig SON MNCs appears to serve an excitatory role, bringing cells closer to firing threshold.
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PMID:Electrophysiology of guinea-pig supraoptic neurones: role of a hyperpolarization-activated cation current in phasic firing. 848 2

Oxytocin has been previously shown to augment GnRH-stimulated LH release. However it is currently unknown which intracellular mediators participate in the process. In this study, after preincubation with oxytocin for 3 hours, quartered pituitaries were stimulated for 15 minutes with GnRH. The effects of diBucAMP, a cell permeable analog of cAMP, and DDA, an adenyl cyclase inhibitor, on the augmentation by oxytocin were investigated. Although addition of diBucAMP increased GnRH-stimulated LH release, it inhibited the augmentation by oxytocin of the response to GnRH. On the other hand addition of DDA induced an increased augmentation by oxytocin. These results indicate that intracellular cAMP inhibits the augmentory activity of oxytocin, and suggest that oxytocin modulation of GnRH action in vivo would be optimal when the hormonal milieu results in reduced levels of cAMP.
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PMID:Oxytocin augmentation of gonadotropin-releasing hormone-stimulated luteinizing hormone release is modulated by cyclic AMP. 876 Oct 24

It is reported that oxytocin (OT) receptors in bovine granulosa cells decrease in concentration during follicular development. However, the factor or factors that regulate OT receptors are not known. In the present study, we evaluated hormonal control of OT receptors in bovine granulosa cells obtained from small antral follicles (3-5 mm in diameter). Granulosa cells were cultured for 48 h and exposed to FSH, LH, progesterone, and/or estradiol-17beta (estradiol) in the final 15 h of culture. The relative binding of OT decreased to 63% of the control value following treatment with FSH (100 ng/ml). The inhibitory effect of FSH was mimicked by an adenylate cyclase activator, forskolin. In contrast, estradiol (10(-7) M) increased the number of OT receptors by 77% compared with that in untreated controls, without changing binding affinity. The effects of estradiol were dose dependent and were diminished by an estradiol antagonist, tamoxifen (10(-6) to 10(-5) M). Although tamoxifen (10(-5) M) alone did not change OT binding, the stimulatory effects of 10(-9) M and 10(-8) M estradiol were inhibited by treatment with tamoxifen (10(-5) M). Furthermore, when the granulosa cells were exposed to FSH (10 ng/ml) and estradiol (10(-10) to 10(-7) M) in various combinations, estradiol inhibited the reduction of OT receptors by FSH. On the other hand, LH and progesterone did not affect OT binding in the cultured granulosa cells. Additionally, OT secretion from cultured granulosa cells was not changed by any treatment used in the present study. These findings suggest that both FSH and estradiol are significant regulators of OT receptors in granulosa cells during follicular development. FSH might down-regulate OT receptors in this phase, and the inhibitory effects of FSH are mediated by the adenylate cyclase-cAMP-protein kinase A system. Furthermore, estradiol seems to play a role in neutralizing the effects of FSH.
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PMID:Regulation of oxytocin receptors in bovine granulosa cells. 928 92

Porcine endometrial cells (a mixture of epithelial, stromal, and glandular cells) were examined for the presence of oxytocin (OT) receptors using a cell culture system and a 125I-labeled OT antagonist. Binding specificity was tested in displacement studies with various related peptides. Scatchard analyses revealed the presence of a binding site with a dissociation constant (Kd) = 0.9 nM and a capacity of 1.9 fmol/10(5) cells. These cells, which were obtained from prepubertal gilts and thus had not been exposed to endogenous ovarian steroids, were used as a model to evaluate the possible action of ovarian steroids and intracellular cAMP on OT receptors. Although ovarian steroids showed no effect on OT receptors, forskolin (an adenylate cyclase activator) and dibutyryl cAMP caused 1.5- to 1.6-fold increases in specific binding of OT without changing the binding affinity. When the endometrial cells were exposed to OT (0.1-1000 nM) in combination with arachidonic acid (10 microM), OT stimulated prostaglandin F2 alpha secretion in a dose-dependent manner. These results indicate the presence of functional OT receptors in prepubertal porcine endometrial cells and suggest that the concentration of OT receptors may be regulated by one or more substances that raise intracellular cAMP levels.
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PMID:Up-regulation of oxytocin receptors in porcine endometrium by adenosine 3',5'-monophosphate. 931 72

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