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

Human luteal cells are known to interact in an auto- and paracrine fashion using a variety of substances, including prostaglandins (PGs), steroids, and peptides. In cultures of dispersed luteal cells obtained from several animal species prostaglandin F2 alpha (PGF2 alpha) and oxytocin (OXT) inhibit progesterone (P) secretion, indicating a luteolytic effect of these substances. The disadvantage of luteal cell cultures is that the different luteal cell types do not communicate with each other, i.e. auto- and paracrine effects cannot be studied. Therefore, we used a microdialysis tubing, which is implanted in human corpora lutea (CL) kept under short term organ culture conditions. Ringer's solution is pumped through the dialysis tubing, and substances secreted by the luteal tissue can be determined in the effluent fractions. This system also allows topical application of substances with putative intraluteal effects. In the present report we used PGF2 alpha, OXT, and estradiol (E2) to examine the effects of these substances on the respective other hormones and on P release from young human CL. Intraluteal application of PGF2 alpha stimulated OXT, E2, and P release. OXT was stimulatory to E2 and P secretion, an effect that can be blocked by a specific OXT antagonist and by tamoxifen. Elevation of intraluteal E2 concentrations also had marked stimulatory effects on P secretion. From luteal cell culture experiments it is known that PGF2 alpha and OXT have direct inhibitory effects on P production, but both substances stimulate E2 release. It was also shown that E2 counteracts the inhibitory effects on P release. Therefore, the PGF2 alpha- and OXT-induced E2 release may be responsible for the increased P release. This assumption is further substantiated by the observation that intraluteally applied E2 stimulates P secretion, and preexposure of human CL to tamoxifen prevents the OXT-induced stimulation of P, but not E2, secretion. We conclude that in young human CL, PGF2 alpha and OXT have dual effects: direct inhibitory effects on P release and E2-mediated stimulatory effects, which in young CL result in a net stimulation of P secretion.
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PMID:Paracrine actions of oxytocin, prostaglandin F2 alpha, and estradiol within the human corpus luteum. 173 Aug 9

A microdialysis system (MDS) was implanted in corpora lutea (CL) from cows (Days 5-7, 8-12, and 15-18 of the estrous cycle); the CL were maintained in organ culture chambers. With this system, active substances can be applied, and a collection of steroids released from luteal cells surrounding the microcapillary (cut-off point = 100 kDa) is possible, while luteal cells maintain cell-to-cell contact. Spontaneous pulses of progesterone release were observed in 90% of control (perfused with Ringer's solution only) at 60-80 min intervals. The infusion of bovine LH (bLH) for 20 min (0.1-10 micrograms/ml) stimulated dose-dependent release of progesterone. Both results indicate that the CL maintains the activity of progesterone release and the ability to respond to LH stimulation in this system. Oxytocin (1-100 microM) also stimulated progesterone release in a dose-dependent manner. Preexposure with oxytocin antagonist blocked the stimulatory effect of oxytocin (p less than 0.01) but not of LH (p less than 0.05), confirming the specificity of the effect. When CL were prestimulated with a low dose of oxytocin (1 microM, 20 min) twice before bLH application, the release of progesterone by bLH (1 micrograms/ml, 20 min) was more pronounced (p less than 0.05). A long-term infusion (3 h) with oxytocin and/or bLH stimulated the release of progesterone for the whole period of time. Oxytocin was most stimulative during the early luteal phase (Days 5-7) and decreased continuously from Days 8-12 to Days 15-18.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Oxytocin stimulates progesterone release from microdialyzed bovine corpus luteum in vitro. 187 90

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

A microdialysis system (MDS) was surgically implanted into the corpora lutea (CL) of 12 normally cycling Holstein heifers. Heifers were either allowed to undergo spontaneous luteolysis (Spontaneous, n = 6) or received an intramuscular injection of prostaglandin F2 alpha (PGF2 alpha) on Day 12 of the estrous cycle (Induced, n = 6). The MDS was implanted on Day 11 in the induced heifers and on Day 17 in Spontaneous heifers. CL were perfused with Ringer's solution at a flow rate of 3 ml/hr beginning immediately after surgery. Dialysate samples were collected hourly for 3-4 days. Samples were assayed for progesterone (P4), oxytocin (OT), PGF, and leukotrienes B (LTB) and C (LTC). Dialysate OT was undetected in all but one Spontaneous and one induced heifer. Lipoxygenase products of arachidonic acid (AA) metabolism (LTB and LTC) in the dialysate were found to be closely associated with luteal regression. In Spontaneous heifers, the mean interval from the first hormone peak to the onset of P4 decline was similar for PGF, LTB, and LTC, with the first peak occurring at 12.8 +/- 8.1, 22.0 +/- 6.1, and 11.0 +/- 8.9 hr before the onset of P4 decline, respectively. The peak LTC value was greater (P < 0.05) than peak LTB or PGF. The 12-hr sampling interval with the highest LTC peak frequency was highly correlated (r = 1.0; P < 0.01) with the onset of P4 decline, but the highest LTB and PGF peak frequencies were not associated with the onset of P4 decline. Indeed, the mean numbers of PGF and LTB hormone peaks were higher (P < 0.05) after the onset of P4 decline than before. Administration of PGF2 alpha on Day 12 of the estrous cycle stimulated a decline in P4 secretion and an increase in the secretion of PGF, LTB, and LTC from the CL. In induced animals, the peak level of PGF was greater (P < 0.05) than peak LTB. These results suggest that the AA metabolites LTB and, especially, LTC play important roles during normal regression of the bovine CL.
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PMID:Roles of leukotrienes in bovine corpus luteum regression: an in vivo microdialysis study. 931 13

To investigate the involvement of oxytocin in their short-term lasting olfactory memory performance, adult female Wistar rats (n = 12) were tested for their juvenile discrimination abilities. As measured by their exploratory behavior towards juveniles, the adult rats were able to discriminate between a previously exposed juvenile and a novel one as long as the interval between the two exposures was less than 180 min. This ability was maintained across all days of the estrous cycle and was unaffected by intracerebroventricular administration of synthetic oxytocin (1 ng/5 microl Ringer's solution) or Ringer's solution immediately after the first exposure. However, treatment with the oxytocin receptor antagonist des-Gly-NH2 d(CH2)5[Tyr(Me)2Thr4]OVT interfered with the ability to establish this kind of olfactory memory although the vasopressin V1 receptor antagonist d(CH2)5Tyr(Me)AVP (100 ng/5 microl each) via the same route did not. This suggests that within a narrow range of concentrations endogenous oxytocin, but not vasopressin, is critically involved in short-term olfactory memory for juvenile conspecifics in female rats. These data are discussed in the light of sexual dimorphic brain development.
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PMID:Endogenous oxytocin is involved in short-term olfactory memory in female rats. 952 Feb 16

Methodological aspects of the use of X-ray microanalysis in physiological and pharmacological experiments on cultured myometrial cells were investigated. Cultured human myometrial cells were grown from biopsies after detaching the fibroblasts. Of the cultured cells, 95-98% showed desmin-like immunoreactivity. Transmission electron microscopy showed that subcultured cells were different from myometrial cells in situ. The effects of washing the cells to remove external salt-rich medium were investigated. All solutions removed the external medium, resulting in lower concentrations of Na and Cl. In the cells washed with 0.3 M mannitol, most of the elemental concentrations were significantly lower than in their unwashed counterparts and those washed in the other solutions. In cells washed in either 0.15 M ammonium acetate or distilled water, no significant differences in P and K compared with their unwashed counterparts were found. There were also no significant differences between cells washed in ammonium acetate and in distilled water. In subsequent experiments ammonium acetate was used. Incubation of cells in standard Ringer's solution resulted in an increase in Na and Cl, and a decrease in K, concomitantly with an increase in Ca. Although Ringer's solution per se can elicit changes in diffusible elements in the cells, physiological and pharmacological effects of oxytocin could still be detected in Ringer's solution. However, effects of oxytocin were different when the experiment was done in culture medium, instead of in Ringer's solution.
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PMID:Preparation of cultured smooth muscle cells from human myometrium for X-ray microanalysis. 985 62

Distal kidney cells (A6) from Xenopus laevis were cultured to confluency on porous supports. Tissues were mounted in Ussing-type chambers to measure short-circuit current (Isc), transepithelial conductance and capacitance, and to analyse the fluctuation in Isc. In the absence of apical NaCl, but with normal basolateral NaCl Ringer's solution, extracellular addition of ATP, oxytocin, a membrane-permeant cAMP derivative, and forskolin produced a transient increase of the electrical parameters. Noise analysis revealed a spontaneous Lorentzian component. All responses depend strictly on the presence of basolateral Cl- and are caused by the activation of an apical (CFTR type) Cl- permeability. Repetitive treatment with ATP (or oxytocin) resulted in refractoriness. ATP and oxytocin acted antagonistically, whereas cAMP and ATP had additive effects. Incubation with the vesicular Ca2+ pump inhibitor thapsigargin or application of the Ca2+ channel blocker nifedipine elicited finite but variable Cl- channel activity. After treatment with nifedipine or thapsigargin, the response to oxytocin was severely impaired. We speculate that not only cAMP but also cell Ca2+ plays a crucial role in the activation of CFTR in A6. Ca2+ may be multifunctional but the rise in capacitance (apical area) observed with all stimulants strongly suggests its involvement in, and contribution to, exocytosis in the process of the CFTR-mediated transcellular Cl- movements.
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PMID:Secretory apical Cl- channels in A6 cells: possible control by cell Ca2+ and cAMP. 1039 65

Adult male Brattleboro rats were used to investigate the impact of the congenital absence of vasopressin on the release pattern of oxytocin (OXT) within the hypothalamic supraoptic nucleus (SON) in response to a 10-min forced swimming session and osmotic stimulation. Both immunohistochemical and in situ hybridisation data suggest that vasopressin-deficient animals have more oxytocin-synthesising neurones in the SON than homozygous wild-type controls. Unexpectedly, both forced swimming and peripheral osmotic stimulation resulted in a blunted release profile of oxytocin within the SON of vasopressin-deficient rats compared to controls. A similar intranuclear OXT response to direct osmotic stimulation of the SON by retrodialysis with hypertonic Ringer's solution in both genotypes confirmed the capability of SON neurones to locally release oxytocin in vasopressin-deficient rats, indicating an altered processing of information originating from multisynaptic inputs rather than a deficit in release capacity. Taken together with data obtained in previous studies, the present findings provide evidence suggesting that autocrine and paracrine signalling of magnocellular neurones differs within the paraventricular nucleus and the SON. Thus, significant alterations in intra-SON oxytocin mRNA levels cannot easily be extrapolated to intranuclear release profiles and the local signal intensity of this neuropeptide after physiological stimulation.
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PMID:Oxytocin in Brattleboro rats: increased synthesis is contrasted by blunted intrahypothalamic release from supraoptic nucleus neurones. 2365 37

The objective of this study was to evaluate the physical and chemical stability of oxytocin 0.08 U/mL admixed in 5% dextrose injection, 0.9% sodium chloride injection, and lactated Ringer's injection bags. Triplicate test samples of oxytocin 0.08 U/mL in each infusion solution were prepared by adding the required amount of oxytocin injection to bags of the three infusion solutions. The samples were stored protected from light and evaluated at appropriate intervals for up to 90 days at room temperature (near 23 deg C). Physical stability was assessed by using an evaluation procedure that included both turbidimetric measurement and visual inspection. Chemical stability was assessed by using a stability-indicating high-performance liquid chromatographic analytical technique and was based on the determination of drug concentrations initally and at appropriate intervals over the study period. The oxytocin admixtures in 5% dextrose and 0.9% sodium chloride were clear and colorless when viewed in normal fluorescent room light and when viewed with a Tyndall beam initially and throughout 90 days. Measured turbidity was low initially and exhibited little change throughout the study. High-performance liquid chromatographic analysis revealed that little or no decomposition occurred in the samples. Oxytocin in the infusion solutions remained stable at room temperature for 90 days. The lactated Ringer's injection samples remained clear and colorless for up to 28 days. However, after that time a small amount of white fluffy microprecipitate developed in two of the three samples by the 35-day observation point. High-performance liquid chromatographic analysis revealed that oxytocin remained stable in lactated Ringer's injection for 28 days at room temperature; substantial losses of oxytocin occurred in all three samples after that time, with about 10% loss at 35 days and up to 21% loss at 60 days. Oxytocin 0.08 U/mL in 5% dextrose injection or 0.9% sodium chloride injection is physically and chemically stable for at least 90 days at room temperature. However, oxytocin in lactated Ringer's injection should be restricted to a use period no greater than 28 days at room temperature to avoid microprecipitate formation and drug loss.
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PMID:Extended stability of oxytocin in common infusion solutions. 2397 90

It has been shown by means of Bentley'sin vitro preparation of the isolated urinary bladder of the toad,Bufo marinus paracnemis Lutz, that bradykinin reversibly inhibited the increase brought about by vasopressin on the permeability to water of the toad bladder. The increased hydro-osmotic response of the bladder to oxytocin was also inhibited by the kinin. The effect on water permeability was observed when bradykinin was added either to the serosal Ringer's solution or to the mucosal solution. The addition of bradykinin alone did not alter the basal osmotic water transfer across the bladder. In this context, bradykinin acted as a competitive antagonist of vasopressin (and oxytocin). Although lacking intrinsic activity, bradykinin exhibited affinity for receptor sites that are also common to the neurohypophysial hormones, causing a parallel shift of the log-dose/response curve for vasopressin without changing the maximal responses. The effects of other kinins (namely kallidin, eledoisin and physalaemin) on the toad bladder were also tested. Each of these drugs alone did not change the basal water flux across the bladder wall. Like bradykinin, these peptides inhibited the increase in water permeability evoked by vasopressin and oxytocin in the bladder. In view of the importance of neurohypophysial hormones and their target tissues to the osmotic homeostasis of amphibians, and the observation of antagonism between the kinins and the pituitary hormones coupled to the abundance of kinins in the amphibian organism, particularly in the skin and urinary bladder, teleological reasoning predicts a physiological role for the kinins, possibly functioning to dampen excesses and oscillations in membrane permeability that could occur in face of a constant and variable secretion of neurohypophysial hormone, thus adding to the homeostatic response of the amphibian organism.
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PMID:Inhibition of the permeability response to vasopressin and oxytocin in the toad bladder: Effects of bradykinin, kallidin, eledoisin, and physalaemin. 2417 37


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