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

Release of oxytocin from the rat posterior pituitary lobe incubated in situ and from the hypothalamic end of the cut pituitary stalk. Acta Physiol. Pol., 1978, 29 (2):97--105. Using the method of incubation in situ of the posterior pituitary lobe and washing the hypothalamic end of the divided pituitary stalk the activity of neurosecretory neurons was investigated directly. The oxytocic activity of the fluid incubating in situ the posterior pituitary lobe or washing the hypothalamic end of the cut pituitary stalk was determined on the rat myometrium. The oxytocic activity disappeared from this fluid after inactivation with sodium thioglycolate. The samples of the fluid incubating the posterior pituitary lobe obtained at 30 min intervals showed alternatingly increased or decreased oxytocic activity. In the fluid washing the cut pituitary stalk the activity was highest from 31 to 60 minutes after division of the stalk.
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PMID:Release of oxytocin from the rat posterior pituitary lobe incubated in situ and from the hypothalamic end of the cut pituitary stalk. 65 29

When Rana cancrivora were collected from fresh water and dehydrated (weight loss 4-10%) by exposure to saline, the plasma titre of hydro-osmotic activity, measured by amphibian bladder assay, was increased three-to fourfold. This activity, which was abolished by thioglycollate and by incubation with tyrosinase or trypsin, was ascribed to vasotocin. The plasma vasotocin activities (hydrated and dehydrated frogs respectively) were estimated to be 0-03-0-5 and 0-15-0-25 mug/1; if referred to oxytocin as a standard the equivalent values were 10 and 30-60 mu./ml. Assuming that the increase represented released pituitary hormone, the amount of vasotocin released by osmotic dehydration was calculated to be of the order of 1 ng. Pituitary glands of hydrated and dehydrated frogs were estimated to have 0.15 and 0-18 mug vasotocin/gland respectively. The possible physiological function of released vasotocin in promoting reabsorption of urea from the urinary bladder is discussed in relation to the euryhaline ability of R. cancrivora.
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PMID:Vasotocin-like activity in the plasms of the euryhaline frog (Rana cancrivora) after transfer from fresh water to saline. 81 47

Previous studies have indicated the existence of natriuretic factors of hormonal nature with the posterior pituitary gland as a possible site of origin. It was in this light that a series of experiments was designed to examine the posterior pituitary for such factors. Acetic acid extracts of porcine and bovine posterior pituitary lobe tissue were subjected to gel filtration on Sephadex G-25. Several fractions in the molecular size range of 1000 were obtained which possessed potent natriuretic activity as assayed in rats. The activity of these fractions maximally increased sodium excretion to 6-8 muequiv./min, a 10- to 40-fold increase above control, when administered intraperitoneally to hydropenic, conscious rats. However, oxytocin and vasopressin, present in the posterior pituitary are natriuretic. These hormones were measured by radioimmunoassay, and invariably only those fractions which contained vasopressin and (or) oxytocin possessed natriuretic activity. Moreover, the extent of the natriuresis could be accounted for by the vasopressin and (or) oxytocin content of the test fractions. The natriuretic property of this material was abolished by treatment with thioglycollate. Further purification of natriuretic fractions by ion exchange resins, thin-layer chromatography and isoelectric focusing failed to resolve natriuretic activity from vasopressin and oxytocin. Similar results were observed following analysis of fractions isolated by gel filtration of acetic acid extracts of ventral hypothalamus tissue. The natriuretic fractions isolated from hypothalamic tissue were indistinguishable from oxytocin and vasopressin. These experiments suggest that the natriuretic activity in neurohypophyseal extracts can be attributed to oxytocin and vasopressin.
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PMID:Characterization of natriuretic activity from posterior pituitary lobes. 97 83

Cumulative concentration-effect curves of oxytocin alone and with various antagonists were obtained in vitro on uteri from estrogen-treated rats. Graded concentrations of salbutamol, isoproterenol, papaverine, theophylline, thioglycollate, and MgCl2 produced a decrease in the maximal effect of oxytocin and a shift of the concentration-effect curves to the right. Salbutamol and isoproterenol appeared to act as functional antagonists of oxytocin in which agonist and antagonist each interacted with its own specific receptor to produce a decreased combined effect on a common effector. Antagonism by papaverine or theophylline was increased by prior or simultaneous treatment with salbutamol, isoproterenol, epinephrine, or norepinephrine. The potentiation had a rapid onset, was partially blocked by propranolol, persisted for at least 85 minutes following washout of salbutamol, and was not due to a residual effect of salbutamol. This interaction could result from phosphodiesterase inhibition by papaverine and the accumulation of higher levels of cyclic 3',5'-adenosine monophosphate brought about by adenyl cyclase activation with the sympathomimetic amines.
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PMID:Antagonism of the uterotonic action of oxytocin in vitro. 111 25

A substance possessing milk-ejecting activity has been isolated from an acetone powder preparation of bovine posterior pituitary glands by Sephadex G-25 chromatography of the neurophysin-neurohypophysial hormone complex. While the material possessed an oxytocic activity of 2.8 IU/mg as measured on the isolated rat uterus, the milk-ejecting activity was more than three fold greater, 9.6 IU/mg. The peptide had an antidiuretic activity of 0.133 IU/mg and a pressor activity of 0.083 IU/mg. Neither the uterine-stimulating action nor the pressor activity was destroyed by incubating the peptide with 0.01 M sodium thioglycollate at 65 degrees C for 5 min. The oxytocic activity was antagonized neither by 1.4 X 10(-6) M atropine nor 3.3 X 10(-7) M phenoxybenzamine.
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PMID:Isolation and some observations of the properties of a bovine neurohypophysial milk-ejecting factor. 122 14

Purified acetic acid extracts of corpora lutea (CL) of non-pregnant goats were found to contain substantial amounts of oxytocin (OT) as measured by radioimmunoassay. OT standard and the CL extracts released prostaglandin F2 alpha (PGF2 alpha) from rat isolated uteri in a quantitatively similar manner. Treatment of both OT standard and CL extract with sodium thioglycolate, oxytocin antiserum or oxytocin antagonist abolished this biological activity. Acid extracts of CL of pregnant goat were found to contain approximately 2% of levels during the cycle by day 21 after fertile mating and this had a reduced ability to release PGF2 alpha from rat uterus. It is concluded that both the immunoreactivity and the biological activity of the CL extracts are due to the presence of an oxytocin-like substance and that tissue levels of oxytocin are low in pregnant compared to non-pregnant goats.
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PMID:Evidence for the presence of oxytocin in the corpus luteum of the goat. 345 13

Incubation with thioglycollate destroyed biologic activity of oxytocin, but left immunologic activity intact. Incubation with plasma of pregnant women at term or with placental extract destroyed biologic and immunologic activities. Dissociation of biologic from immunologic sites is suggested.
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PMID:Oxytocin: effects of degradation on radioimmunologic and biologic activity. 534 87

Identifying posterior pituitary hormones in body fluids or neurohypophysial extracts was heretofore partially achieved by using pharmacologic potency ratios or semispecific inactivation by thioglycolate or enzymes. Production of antisera against oxytocin and lysine-vasopressin has prompted us to test their specificity against lysine-vasopressin, arginine-vasopressin, arginine-vasotocin, and oxytocin. In ethanol anesthetized rats, antidiuretic and milk-ejection activities were assayed for each peptide-antiserum combination after 0, 30, 60, and 90 min of incubation. Results indicate that (a) oxytocin antiserum inactivates oxytocin, but not arginine-vasopressin, lysine-vasopressin, or arginine-vasotocin; vasopressin antiserum inactivates arginine-vasopressin and lysine-vasopressin, but neither oxytocin nor arginine-vasotocin; (b) an identifiable antigenic site exists for each hormone; (c) relatively specific identifications of natural neurohypophysial peptides are possible using antisera and bioassays; (d) this method is promising for identifying neurohypophysial peptides in body fluids and pituitary extracts; and (e) active and passive immunization against oxytocin and vasopressin may increase our understanding of their physiologic functions.
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PMID:Identification of neurohypophysial hormones with their antisera. 544 83

1. An oxytocic substance has been isolated from ox hypothalamus by successive gel filtration on Sephadex G-25 and Sephadex G-50, and its pharmacology has been examined on three smooth muscle preparations.2. The substance has the same order of potency on rat uterus, guinea-pig ileum, and hen rectal caecum.3. The action of the substance on rat uterus was not abolished by thioglycollate.4. Atropine (1.0 mug/ml.), phenoxybenzamine (0.1 mug/ml.) and mepyramine (1.0 mug/ml.) did not block the smooth muscle action of the substance.5. Drug action, relative potency, and log dose-response relationships distinguish the substance from 5-hydroxytryptamine, acetylcholine, oxytocin, vasopressin, angiotensin amide, bradykinin, and purified preparations of substance P.
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PMID:The pharmacology of a new oxytocic principle from ox hypothalamus. 581 85

In diabetes insipidus (DI) rats, electrical stimulation of the posterior pituitary lobes in vitro promotes the release of corticotropin-releasing factor (CRF). The CRF activity is abolished by preincubation of the posterior lobe media with thioglycolate. Oxytocin, which is released concomitantly into the medium (3.2 mIU/lobe/20 min), accounts for the complete CRF effect. Neural lobe extracts from DI and normal rats contain 40-70% more CRF activity than can be explained by their content in vasopressin and/or oxytocin. The discrepancy between released and extracted CRFs suggests that hypothetical CRFs or potentiating factors are not released from nerve endings or have to be present in high concentrations to manifest their effect.
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PMID:Oxytocin: major corticotropin-releasing factor secreted from diabetes insipidus rat posterior pituitary in vitro. 625 96


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