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)

Human amnion is hypothesized to be a target tissue for hormone messages from the fetus regarding labor. We have previously demonstrated prostaglandin E2 (PGE2) release in amnion after treatment with phorbol and oxytocin, but other potential agonists of the inositol phospholipid/protein kinase-C system have not been investigated. The effects of extracellular ATP on cytosolic calcium concentration [( Ca2+])i) inositol phosphate (IP) accumulation, and PGE2 production were studied in cultured human amnion cells. Intracellular free calcium [Ca2+]i was measured using the fluorescent dye fura-2. Addition of 0.01-30 microM ATP resulted in a [Ca2+]i transient which peaked within 15 sec and returned to baseline over 10 min. UTP (1 microM) was more effective than ATP (1 microM); [Ca2+]i levels rose from 233 to 2880 nM (UTP) and 2320 nM (ATP). A reduced effect was observed with other nucleotides in a rank order of agonist potency of ITP greater than CTP greater than ADP greater than GTP greater than TTP. No effect was seen with AMP, cAMP, or adenosine. This is consistent with P2 purinoceptors, as described in other tissues. ATP (100 microM) also dramatically increased IP accumulation. Inositol triphosphate, inositol bisphosphate, and inositol monophosphate were increased 7-, 9-, and 16-fold respectively. The agonist potency order of other nucleotides for IP accumulation was the same as that of [Ca2+]i. Pharmacological concentrations of ATP (1 mM) were required to increase PGE2 production. Many other nucleotides were equally effective at this concentration. ATP activates the phospholipase-C system in human amnion, as demonstrated by the increase in [Ca2+]i and inositol phosphates. The physiological significance of purinergic stimulation of this tissue remains unclear.
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PMID:Adenosine triphosphate activates the phospholipase-C cascade system in human amnion cells without increasing prostaglandin production. 292 32

Synaptic plasma membranes containing binding sites for tritiated oxytocin and arginine vasopressin were isolated from rat hippocampus. The binding parameters for oxytocin and vasopressin sites were determined and statistically analysed. The fitted curve for oxytocin binding was compatible with a model where the ligand interacts with two classes of receptors with different capacities and affinities. The sites with low binding capacity had an apparent dissociation constant at equilibrium of 1.8 nM and a maximal binding capacity of 17 fmol/mg protein. By contrast, the Scatchard plot failed to reveal a marked heterogeneity in the population of sites labelled with [3H]vasopressin with an affinity of 1.5 nM and a maximal binding capacity of 39 fmol/mg protein. The specificity of these binding sites, tested in competition experiments, revealed that these neurohypophyseal hormones labelled two distinct populations of sites. One population with a high affinity for vasopressin, oxytocin and vasotocin, the other population with a high affinity for vasopressin and vasotocin and a low affinity for oxytocin. Adenylate cyclase activity was not affected by arginine-vasopressin or oxytocin. These receptors are compared with previously characterized peripheral receptors.
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PMID:Pharmacological characterization of two specific binding sites for neurohypophyseal hormones in hippocampal synaptic plasma membranes of the rat. 299 30

The neurohypophysial hormones oxytocin (OT) and vasopressin (VP) are involved in the regulation of the contractility of the male genital tract in several animal species. We investigated the presence of specific binding sites for [3H]OT and [3H]arginine VP (AVP) in membranes prepared from tunica albuginea, epididymis, and vas deferens from prepubertal pigs 2-16 weeks of age. Membranes were incubated with [3H]OT and [3H]AVP in the presence or absence of the corresponding unlabeled peptides. Binding equilibrium was reached in 60 min at 22 C. Millimolar concentrations of Mg2+ increased the specific binding of both ligands. Analysis of families of self- and cross-displacement curves using the computer program LIGAND clearly demonstrated that two classes of binding sites were present in all tissues investigated. The first class of sites, designated the OT site, shows high affinity for OT, AVP, lysine vasopressin, arginine vasotocin, the selective OT agonists [Thr4,Gly7]OT and [Asu1,6]OT, and the OT antagonists derived from ornithine vasotocin (OVT), namely d(CH2)5Tyr(Et)OVT and dEt2OVT. The second class of sites, designated the VP site, shows high affinity for AVP, lysine vasopressin, arginine vasotocin, and the selective V1 antagonist d(CH2)5Tyr(Me)AVP. The V2 agonist [1-deamino,4-valine]8-D-AVP shows low affinity for both sites. Isotocin, desglycinamide [Arg-8]AVP and tocinoic acid were ineffective in displacing [3H]AVP or [3H]OT. The highest density of OT receptors was found in tunica albuginea and epididymis, whereas the highest density of AVP receptors was found in vas deferens. Adenylate cyclase was not activated in any of the tissues studied by concentrations of AVP or OT up to 100-fold greater than their Kd values. This is the first demonstration and pharmacological characterization of specific OT and V1 VP receptors in the tunica albuginea, epididymis, and vas deferens. The recent demonstration of high local concentration of neurohypophysial hormones in the gonads of several mammals support a physiological role of these OT and VP receptors in regulation of the motility of the male genital tract.
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PMID:Identification and characterization of two classes of receptors for oxytocin and vasopressin in porcine tunica albuginea, epididymis, and vas deferens. 302 94

WRK 1, a cloned cell line derived from a rat mammary tumour, carries specific vasopressin-binding sites. Specific binding of 2-tyrosine-3H-labelled [8-lysine]vasopressin ([3H]vasopressin) was time-dependent, saturable and reversible. Scatchard-plot analysis of hormone binding indicated the presence of a single class of receptors with an equilibrium dissociation constant of 12.7 +/- 0.2 nM. The maximal binding capacity was 75 +/- 6 fmol/10(6) cells, which corresponds to approx. 45,000 sites per cell. Oxytocin and a highly potent oxytocin analogue were able to inhibit completely [3H]vasopressin binding, but, in this respect, they were far less potent than vasopressin. This clearly demonstrates the vasopressinergic nature of this receptor. Pharmacological studies using a series of 14 vasopressin or oxytocin analogues indicated that the ligand selectivity of the vasopressin receptor found on WRK 1 cells resembles that of the rat hepatocyte. This signifies that this vasopressin receptor is of the V1a subtype. This conclusion was confirmed by the observation that vasopressin did not influence the production of intracellular cyclic AMP in WRK 1 cells.
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PMID:Characterization of specific V1a vasopressin-binding sites on a rat mammary-tumour-cell line. 303 Feb 77

ACTH, isoprenaline, forskolin, and dibutyryl cyclic AMP prevented insulin from stimulating adipocyte pyruvate dehydrogenase in the presence of adenosine deaminase. Antagonism was reversed by N6-phenylisopropyladenosine as well as oxytocin. The stimulatory effects of insulin, adenosine and oxytocin on adipocyte pyruvate dehydrogenase appear to be through (a) mechanism(s) which is (are) similar or related.
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PMID:Adenosine and oxytocin reverse antagonism of cyclic AMP elevating agents to insulin activation of adipocyte pyruvate dehydrogenase. 303 Aug 21

Carp (Cyprinus carpio) liver maintained normal glycogen content and enzyme complement for several days in organ culture. Epinephrine-stimulated glycogenolysis, phosphorylase activation, and cyclic AMP (cAMP) accumulation in a concentration-dependent manner with EC50s of 100, 100, and 500 nM, respectively. These actions were blocked by the beta-adrenergic antagonist, propranolol, but not by the alpha-adrenergic antagonist phentolamine. Glycogenolysis and tissue cAMP were uninfluenced by 10(-6) M arginine vasotocin, arginine vasopressin, lysine vasotocin, lysine vasopressin, mesotocin, or oxytocin, but were slightly increased by 10(-5) M isotocin and slightly decreased by 10(-6) M angiotensin II. [125I]-iodocyanopindolol (ICP), a beta-adrenergic ligand, bound to isolated carp liver membranes with a KD of 83 pM. Maximum binding of 45 fmol/mg protein was at 600 pM. Propranolol, isoprenaline, epinephrine, phenylephrine, norepinephrine, and phenoxybenzamine displaced ICP with KDs of 100 nM, 2, 20, 20, 60, and 200 microM, respectively. The alpha-adrenergic antagonists, yohimbine and prazosin, showed no specific binding. These data provide evidence that catecholamines act via beta-adrenergic receptors in carp liver and that alpha-adrenergic receptors are not present. Vasoactive peptides play no significant role in regulation of carp liver glycogenolysis.
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PMID:Hormonal regulation of hepatic glycogenolysis in the carp, Cyprinus carpio. 303 3

The hypothalamic-pituitary-adrenocortical axis is activated in pregnancy and parturition. Levels of immunoreactive corticotrophin releasing factor (irCRF), immunoreactive adrenocorticotropic hormone (irACTH) and cortisol concentrations in maternal plasma are elevated throughout gestation, increase further during labour and fall precipitously after parturition. The placenta contains biologically active CRF and ACTH and it has been suggested that the placenta produces these peptides during pregnancy. Here we show that irCRF is located in the cytotrophoblast cells of placenta collected at term. Using a monolayer primary culture of human placental cells we have found that CRF stimulates secretion of peptides containing the ACTH sequence in the placenta in a dose-dependent manner, as it does in the pituitary. This effect is reversed by a CRF antagonist and is mimicked by dibutyryl cyclic AMP and forskolin. Glucocorticoids, which suppress the secretion of pituitary ACTH, were found to have no influence on release of irACTH by the placenta. Oxytocin and prostaglandins stimulate irACTH and irCRF secretion from cultured placental cells and the irACTH-releasing activity of two prostaglandins is partially reversed by a CRF antagonist. Thus CRF may be involved in the paracrine regulation of placental irACTH secretion.
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PMID:Evidence for local stimulation of ACTH secretion by corticotropin-releasing factor in human placenta. 303 77

Corpora lutea from sheep and cows as well as human and primates contain both large and small steroidogenic cells exhibiting distinct functional properties. Only the small cells seem to be able to respond in vitro to LH stimulation by raising their progesterone secretion. However, the entire progesterone secretion of the corpus luteum has been shown to be regulated in vivo by LH in the primate. The LH steroidogenic action involves the activation of membrane adenylate cyclase whose molecular mechanism has been elucidated. Then a rise in intracellular cyclic AMP induces phosphorylation by a cyclic AMP dependent protein kinase of steroidogenic protein targets which have not yet been completely identified. In sheep and cows, luteolysis is believed to be the consequence of a series of reciprocal interactions between the corpus luteum whose large cells secrete pulses of oxytocin in response to PGF2 alpha luteolysin and the endometrium which secretes pulses of PGF2 alpha in response to oxytocin. The secretion of endometrial PGF2 alpha can only begin after the induction of endometrial receptors by estradiol, from the preovulatory follicles. Similarly in women and primates luteolysis, which does not require the presence of the uterus, could be the consequence of local reciprocal paracrine interactions between luteal cells of different types. These interactions are likely to involve PGF2 alpha' oxytocin and estradiol. The biochemical mechanism responsible for the inhibition by PGF alpha of LH induced progesterone secretion in luteal cells could involve a stimulation in the cell membrane of protein kinase C and the rise of cytosolic Ca+.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Recent concepts concerning the corpus luteum]. 307 52

Vasopressin, vasopressin analogs, forskolin and 8-bromo-cyclic AMP (8Br-cAMP) were studied for their effects on transepithelial water flux in toad urinary bladder. Arginine vasopressin, arginine vasotocin, oxytocin, desamino-8-D arginine vasopressin, forskolin and 8Br-cAMP stimulated hydro-osmotic water flux in a dose-dependent fashion. The rank order of potency was arginine vasotocin greater than arginine vasopressin greater than oxytocin greater than desamino-8-D-arginine vasopressin greater than forskolin greater than 8Br-cAMP. The vasopressin analogs [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid),2-(O-methyl)tyrosine,8-arginine]vasopressin (SK&F 100273), [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid),2-(O-methyl)tyrosine,4-valine,8-arginine]vasopressin (SK&F 100501), [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid),2-D-tyrosine,4-valine,8-arginine]vasopressin (SK&F 100885), [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid),2-(O-ethyl)tyrosine,4-valine,8-arginine]vasopressin (SK&F 100398), [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid),2-D-isoleucine,4-valine,8-arginine]vasopressin (SK&F 101485), [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid),2-(O-ethyl)-tyrosine,4-valine,8-arginine]vasopressin (SK&F 101498), [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid),2-(O-ethyl)D-tyrosine,4-valine,8-arginine,9-desglycine]vasop ressin (SK&F 101926) and [1-(beta-mercapto-beta-beta-cyclopentamethylene propionic acid),2-D-phenylalanine,4-valine,8-arginine] vasopressin (SK&F 101071) antagonized arginine vasopressin-stimulated water flux and displaced the agonist dose-response relationship to the right in a parallel fashion. The most potent antagonists were those having the (O-ethyl)-D-tyrosine substitution at position 2. None of the antagonists tested had any effect on 8Br-cAMP-stimulated water flux at concentrations up to 10(-6)M.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Mechanism of action and structural requirements of vasopressin analog inhibition of transepithelial water flux in toad urinary bladder. 309 Feb 34

This paper reports the effect of reversing the osmotic environment between luminal and serosal compartments of a toad urinary bladder on the polarity of assembly of tight junction strands. Toad bladders were filled with Ringer's solution (220 mOsm) and were immersed in distilled water at room temperature or at 37 degrees C. Within two minutes, new tight junction strands are assembled. The new tight junctional strands unite the basal pole of epithelial cells with the apical side of basal cells. Physiological studies show that oxytocin, a synthetic analog of antidiuretic hormone, is still capable of inducing increases in water transport in epithelia which were osmotically reversed. This capacity decreases significantly for longer periods of osmotic reversal. Osmotic reversal does not alter the original polarity of epithelial cells: the apical tight junction belt, at the apical pole, is not displaced; the freeze-fracture morphology typical of apical plasma membrane (particle-rich E faces; particle-poor P faces) is not altered; oxytocin and cyclic AMP induce aggregates which are observed only at the apical plasma membrane. Massive assembly of junctional elements occurs even in epithelia preincubated in the presence of cycloheximide (an inhibitor of protein synthesis) or of cytoskeleton perturbers. Our experiments show that the polarity of assembly of tight junction strands depends on the vectorial orientation of the osmotic environment of the epithelium.
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PMID:Osmotic reversal induces assembly of tight junction strands at the basal pole of toad bladder epithelial cells but does not reverse cell polarity. 310 10


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