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)

Radioimmunoassayable plasma and pituitary oxytocin (ROT) was measured during pregnancy and parturition. The highest mean plasma ROT level was seen in maternal rats on day 20 of pregnancy followed by a non significant decrease on day 21 reaching the basal level just before delivery. Plasma ROT level declined continuously up to the time of delivery of the first pup and then gradually increased until the completion of parturition. The highest maternal mean pituitary ROT level was found on day 21 pregnancy. Just before delivery of the first pup, the mean pituitary ROT level significantly declined by 22%. Pituitary ROT level declined steadily during the delivery of the first five pups. This pattern of reduction was reversed and ROT levels increased between the delivery of the fifth pup and the completion of labor. The increase of maternal pituitary and plasma ROT levels during delivery of the pups suggest that maternal ROT may play a role in normal parturition. Fetal hypothalamic-pituitary ROT does not seem to play any part in parturition.
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PMID:Radioimmunoassay of plasma and pituitary oxytocin in pregnant rats during various stages of pregnancy and parturition. 48 18

By using a specific heterologous double-antibody RIA, changes in the blood levels of PRL during pregnancy, pseudopregnancy, and lactation have been investigated for the first time in the rabbit. Blood levels fluctuate during early and midpregnancy in a manner similar to that in pseudopregnancy. Levels decline in the third trimester of pregnancy and increase dramatically (3- to 25-fold) at or 1--2 days before delivery. Pituitary levels of PRL showed no significant alteration, and fetal serum and amniotic fluid levels of PRL remain low (less than 10 ng/ml) throughout pregnancy. No significant PRL-like, GH-like, or placental lactogen-like activity could be demonstrated either in serum or in extracts of placenta (n = 262) taken between days 10 and 31 of pregnancy. Postpartum blood levels of PRL were similar in lactating and postpartum nonlactating females. In lactating females, suckling evoked an immediate increase (15- to 25-fold) in circulating PRL levels. Handling the female or the iv injection of oxytocin during lactation did not cause PRL release. In contrast, manual test stimulation caused an immediate increase in blood levels of PRL and a response pattern very similar to that of natural suckling. These results suggest that PRL release during suckling occurs solely in response to the tactile stimulation of the teats.
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PMID:Prolactin during pregnancy and lactation in the rabbit. 57 Apr 85

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

Observations on water and electrolyte metabolism after hypophysectomy or adrenalectomy, in male and female rats with hereditary hypothalamic diabetes insipidus (Brattleboro strain) are confirmed and extended. The diabetic (homozygous, DI) state relative to the non-diabetic (heterozygous, non-DI) state was characterized by (1) water intake of 55-120% body weight; (2) copious urine hypo-osmotic to plasma; (3) greater excretory rates of total solute, Na, Ca and Mg; (4) similar plasma composition except that in male DI rats, K concentration was less, and in female DI rats osmolarity was higher; (5) glomerular filtration rates (GFR) were similar with close correlations between: food and water intakes, water intake and output, urinary Na and K, Na and Cl, K and Cl, and Ca and Mg; (6) both female DI and non-DI rats had lower urinary Na:K ratios and lower plasma Na concentrations than males; (7) female DI rats excreted relatively larger amounts of K and Cl, and had higher plasma Ca concentrations than other groups. Hypophysectomized DI rats had decreased water intake and urine output, decreased solute excretion, decreased loss of osmotically free water, lower excretory rates of Na, K and Cl, and increased urinary osmolarity and K concentrations. Hypophysectomized non-DI rats had increased urinary excretory rates, decreased solute excretion (by 60-70%), decreased osmotically free water absorption, decreased urinary osmolarity, Na and K concentrations, and increased excretory rates of Ca and Mg. Hypophysectomized DI and non-DI rats had increased plasma osmolarity and Na concentration. Plasma renin activities (PRA) were higher in DI than in non-DI rats with female values lower than those of males; values for both sexes of DI and non-DI rats were reduced after hypophysectomy. Adrenalectomized DI rats had about a 50% reduction in water intake, urine output and free water clearance, increased urinary concentration of electrolytes and total solute by day 4 after operation; their Na balance (dietary:urine) did not change significantly in contrast to adrenalectomized non-DI rats in which a greater percentage of dietary Na appeared in the urine. GFR was similarly reduced in adrenalectomized DI and non-DI rats. Plasma osmolarity increased in adrenalectomized male DI, decreased in female DI and non-DI, and did not change in male non-DI rats. Plasma K concentrations increased after adrenalectomy in all groups, only non-DI rats had a significantly decreased plasma Na concentration. There was no sex difference in pituitary oxytocic activity but it was consistently reduced in DI rats; there was little change after adrenalectomy in male DI and non-DI rats; but there was an increase in DI and non-DI females. Pituitaries of DI rats had no measurable ADH activity (except the inherent activity of oxytocin). Pituitary ADH values for male and female non-DI rats were similar and were unaffected by adrenalectomy.
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PMID:Effects of adrenalectomy and hypophysectomy on water and electrolyte metabolism in male and female rats with inherited hypothalamic diabetes insipidus (Brattleboro strain). 101 Sep 70

Pituitary cells, collected from five healthy dogs, were cultured and treated with various doses of ovine corticotropin-releasing hormone (CRH), arginine vasopressin (AVP), oxytocin (OT), or angiotensin II (AII) to determine which of these hypothalamic peptides affected adrenocorticotropin (ACTH) secretion. Of the 4 peptides, only CRH significantly increased ACTH secretion from cultured canine anterior pituitary cells. The lowest dose of CRH tested, 0.01 nM, significantly stimulated ACTH release. Co-addition of AVP, OT, or AII with CRH did not increase ACTH secretion beyond that caused by addition of CRH alone. Similarly, neither co-addition of AVP with OT, AVP with AII, or OT with AII significantly stimulated ACTH secretion. These results support a role for CRH in the physiologic regulation of ACTH secretion from the canine anterior pituitary, but do not support regulatory roles for AVP, OT, or AII.
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PMID:Regulation of adrenocorticotropin secretion from cultured canine anterior pituitary cells. 133 8

Physiological role and importance of calcium ion has been investigated based on the study of the mechanism of muscle contraction. Furthermore, calcium ion has been proved to have a wide variety of biological roles in hormonal secretion, cell proliferation and reproduction as well as in muscle contraction. In this lecture, I would like to show a method to measure intracellular calcium ion concentrations ([Ca2+]i) and to give a general information about the roles of calcium ion to induce various cell activities. Then I would like to talk about the changes in intracellular calcium concentration ([Ca2+]i) and their meaning in the field of reproductive physiology including uterine muscle contraction, pituitary LH secretion, and fertilization. 1) Uterine muscle contraction and calcium ion The function of calcium ion is most intensively investigated in muscle contraction. We show [Ca2+]i increase in cultured myometrial cells. This increase is inhibited by omission of extracellular calcium or addition of calcium channel blockers. These results support usefulness of Ca2+ channel blockers in treating threatened premature delivery. We also report the action of MgSO4 as an inhibitory agent of [Ca2+]i increase stimulated by oxytocin. 2) Pituitary gonadotropin secretion and calcium ion Pituitary LH secretion is regulated by gonadotropin releasing hormone (GnRH). GnRH induces rapid increases and then sustained releases of LH secretion. By the omission of extracellular calcium, or by addition of Ca2+ channel blockers, the sustained phase of LH secretion is abolished. GnRH also increase [Ca2+]i in a very similar manner to that of LH secretion. The [Ca2+]i increase is essential in LH secretion.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Roles of calcium ion in reproductive physiology]. 140 28

Pituitary oxytocin (OT) secretion is inversely related to saline consumption in several experimental models of sodium appetite in rats. Because systemic OT administration does not inhibit sodium appetite, release of OT as a neurotransmitter within the brain, coincident with its secretion from the pituitary, may be related to inhibition of sodium ingestion. The present studies evaluated this possibility by increasing brain OT concentrations both exogenously and endogenously in rats with hypovolemia produced by subcutaneous administration of polyethylene glycol (PEG) solution. Intracerebroventricular (i.c.v.) administration of OT completely abolished intake of 0.5 M NaCl in PEG-treated hypovolemic rats, but did not significantly affect PEG-stimulated water intakes. Endogenous OT secretion was stimulated by systemic treatment with naloxone, which has been shown to increase peripheral and central OT levels. In both one-bottle (0.5 M NaCl) and two-bottle (water and 0.5 M NaCl) drinking tests, intraperitoneal naloxone completely abolished sodium appetite in association with markedly increased pituitary secretion of OT. This inhibition of sodium appetite could be prevented by i.c.v. pretreatment with a specific OT-receptor antagonist, although the antagonist by itself did not affect PEG-stimulated sodium intake. These findings therefore support previous reports which have found that sodium appetite in rats is inhibited by treatments that elicit pituitary release of OT, and provide more direct evidence that brain OT is causally involved in the inhibition of sodium appetite stimulated by such treatments in rats.
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PMID:Central oxytocin mediates inhibition of sodium appetite by naloxone in hypovolemic rats. 140 80

In the present study we report the properties of vasopressin (VP) receptors in the anterior pituitary gland and show that the number of these receptors is markedly affected by adrenalectomy and hypothalamic lesions. VP-binding activity was assayed in particulate fractions of rat anterior pituitary glands using tritium-labeled arginine VP ([3H] AVP) as tracer. In the presence of Mg2+ the radioligand interacted with a single class of high affinity, low capacity binding sites. Magnesium ions modulated the affinity of the receptors but had no effect on binding capacity. Guanine nucleotides decreased the amount of tracer bound in a dose-dependent manner by increasing the dissociation constant (Kd) of the binding reaction by approximately 2-fold. Increasing the concentration of Mg2+ did not prevent this effect. Bilateral adrenalectomy (ADX) decreased pituitary AVP-binding activity: binding fell by 30% 4 h after surgery and declined further to 10% or less of control at 4 days. The decrease in binding was primarily due to a reduction in the number of receptors. Daily administration of corticosterone inhibited the reduction of binding activity at 4 days in a dose-dependent manner. Destruction of hypophyseotropic VP neurons by means of surgical lesioning of the hypothalamic paraventricular nucleus or the medial basal hypothalamus abolished the effect of ADX on pituitary AVP binding at 24 h but only attenuated the degree of receptor loss at 4 days. Furthermore, the lesions themselves caused a significant (approximately 30%) reduction in receptor number 4-7 days after hypothalamic surgery. Adrenalectomy reduced pituitary AVP-binding activity in homozygous (di/di) Brattleboro rats. The extent as well as the time course of the loss of receptor activity resembled that in normal rats. Rat anterior pituitary segments were exposed to synthetic CRF, AVP, or oxytocin (all 10(-7) M) for 4 h in vitro, and [3H] AVP-binding activity was subsequently determined. Both AVP and oxytocin reduced the amount of radioligand bound, while CRF had no effect. These observations allow the following conclusions: Magnesium ions and guanine nucleotides modulate the affinity of pituitary AVP receptors by different mechanisms and have no effect on binding capacity; Pituitary receptors for AVP are regulated by the amount of AVP released by paraventricular nucleus neurons as well as through a mechanism that requires the presence of corticosterone; Homozygous Brattleboro rats may respond to ADX by increased hypothalamic release of an endogenous ligand for pituitary AVP receptors.
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PMID:Pituitary binding of vasopressin is altered by experimental manipulations of the hypothalamo-pituitary-adrenocortical axis in normal as well as homozygous (di/di) Brattleboro rats. 316 22

To study the regulation of hypothalamic vasopressin (VP) and oxytocin (OT) gene expression in relation to the development of hypertension, levels of VP mRNA and OT mRNA were determined in spontaneously hypertensive rats (SHR). Differences in VP and OT mRNA content of the supraoptic nucleus (SON) and paraventricular nucleus (PVN) of 4- and 10-week-old SHR and Wistar-Kyoto controls (WKY) were quantitated by dot-blot and Northern blot analysis. VP and OT pituitary content and VP plasma levels were measured by radioimmunoassays. VP mRNA levels were approximately 2-fold and 3-fold higher in the SON and PVN of 4-week-old SHR, respectively, as compared to controls. The OT mRNA levels were approximately 35% lower in both nuclei of the SHR. There was no difference in VP and OT pituitary content between 4-week-old SHR and WKY, but VP plasma levels were higher in SHR. In the 10-week-old SHR VP mRNA levels were still approximately 30-40% higher and the OT mRNA levels were approximately 40% lower in both nuclei when compared to age-matched WKY. Pituitary VP and OT contents were respectively 1.5-fold higher and 20% lower in the 10-week-old SHR than in 10-week-old WKY. VP plasma levels were still elevated in the SHR. The data indicate that in the hypothalamo-neurohypophyseal system of the SHR the VP system is in a higher state of activity, while the OT system is lower in activity.
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PMID:Vasopressin and oxytocin gene expression in the supraoptic and paraventricular nucleus of the spontaneously hypertensive rat (SHR) during development of hypertension. 323 90

The response of plasma oxytocin to an iv bolus injection of crystalline insulin (0.15 U/kg) was evaluated in 14 normal weight [mean body mass index (BMI) = 23] and in 9 obese (mean BMI = 42) men. Similar blood glucose decrements after insulin injection were observed in the two groups. Obese and normal weight subjects presented similar basal oxytocin levels. In both groups, oxytocin rose significantly during the insulin tolerance test (ITT); however, the peak oxytocin response in the obese men was significantly lower than in the normal weight subjects. Obese men were restudied after substantial weight loss. Basal oxytocin levels and glucose response to insulin did not change after weight reduction. The oxytocin response to the ITT was significantly higher than before slimming and did not differ from that observed in the normal weight subjects. A significant negative correlation between BMI values and oxytocin peak levels during ITT was observed in the lean controls and obese subjects (r = 0.516, p less than 0.02). These results demonstrate that in obese subjects the oxytocin secretory response during an insulin tolerance test is reduced, suggesting the existence of a hypothalamic-pituitary disorder in obesity.
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PMID:Oxytocin response to insulin-induced hypoglycemia in obese subjects before and after weight loss. 328 8

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