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)

Luliberin, a luteinizing hormone-releasing hormone, was shown to inhibit the respiratory enzymes of rat liver mitochondria and submitochondrial particles prepared from beef heart mitochondria. At the hormone concentration of 8.10(-6) M the NADH-oxidase activity of the submitochondrial particles was inhibited by 50%. The fragments of the hormone and its analogs and pyroglutamic acid, oxytocin and bradikinin possessed practically no inhibiting effects. In the case of submitochondrial particles the inhibition was only observed in the presence of Ca2+ and was significantly decreased after addition of bovine serum albumin and phospholipase inhibitors -- butacaine and dicaine. It is assumed that the effect of luliberin on the respiratory chain is mediated through mitochondrial phospholipase.
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PMID:[Effect of luliberin on the activities of mitochondrial respiratory enzymes]. 38 96

The evaluation of a radioimmunoassay of oxytocin is described. The method involved careful collection and transportation of blood at 4 degrees C, acidification of the plasma, extraction with Fuller's earth and radioimmunoassay using antisera raised in rabbits immunized against oxytocin conjugated to bovine serum albumin and 125I-labelled oxytocin. The antisera showed insignificant cross-reaction with a variety of small peptides including vasopressin and vasotocin. The limit of detection of the assay was 2.5 pg with intra-assay and interassay coefficients of variation of 7-15% and 12-18% respectively. Seventy-seven per cent (88 out of 116) of the pregnant women tested had detectable maternal plasma oxytocin. Serial samples of maternal plasma showed a significant increase in oxytocin from the first to the second stage of labour and a significant decrease in the third stage. Oxytocin concentrations in the umbilical arterial plasma were significantly higher in patients in labour. The significance of these findings is discussed.
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PMID:Radioimmunoassay of oxytocin. 62 20

An experiment was conducted to (i) determine whether administration of recombinant bovine interferon-alpha I1 (rBoIFN-alpha) attenuates oxytocin-induced release of prostaglandin F-2 alpha and (ii) confirm previous observations that rBoIFN-alpha causes acute changes in body temperature and circulating concentrations of progesterone. Cows were treated twice a day from Day 14 to Day 17 after oestrus with a control regimen (bovine serum albumin (BSA), i.m. + BSA intrauterine (i.u.)), rBoIFN-alpha, i.u. + BSA, i.m. (rBoIFN-IU) or rBoIFN-alpha, i.m. + BSA, i.u. (rBoIFN-IM). On Day 17, plasma concentrations of 13,14-dihydro,15-keto-prostaglandin F-2 alpha (PGFM) were measured after injection of oxytocin. Cows treated with rBoIFN-IU and rBoIFN-IM had longer oestrous cycles and luteal lifespans than control cows. A hyperthermic response and decline in plasma concentrations of progesterone was noticed after administration of rBoIFN-alpha on Day 14. On other days, the hyperthermic response was not present and the decline in progesterone was less pronounced. There was no significant effect of rBoIFN-alpha on circulating concentrations of oestradiol between Days 14 and 17. The release of PGFM induced by oxytocin was lower in cows treated with rBoIFN-alpha than in control cows. Oxytocin caused increased plasma concentrations of PGFM in four of five control cows, two of five rBoIFN-IU cows and two of five rBoIFN-IM cows. The peak PGF-2 alpha response to oxytocin (peak value after injection minus mean concentration before injection) was 257.8 +/- 61.3 pg/ml for control cows, 100.7 +/- 40.8 pg/ml for rBoIFN-IU and 124.9 +/- 40.4 pg/ml for rBoIFN-IM. It is concluded that rBoIFN-alpha can reduce oxytocin-induced PGFM release and may therefore extend the lifespan of the corpus luteum by interfering with events leading to luteolytic release of PGF from the uterus. Administration of rBoIFN-alpha can cause acute changes in body temperature and circulating concentrations of progesterone that become less severe after repeated exposure to rBoIFN-alpha.
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PMID:Alteration of oestrous cycle length, ovarian function and oxytocin-induced release of prostaglandin F-2 alpha by intrauterine and intramuscular administration of recombinant bovine interferon-alpha to cows. 178 57

The reactivity toward peptides and proteins of S-(N-methylcarbamoyl)glutathione (SMG), the glutathione conjugate of methyl isocyanate, and the corresponding cysteine adduct, S-(N-methylcarbamoyl)cysteine (SMC), was investigated with the aid of in vitro model systems. Incubation of SMC or a trideuteriomethyl analogue of SMC with either the reduced or oxidized forms of oxytocin afforded similar mixtures of mono-, bis- and tris-N-methylcarbamoylated peptides. Structure elucidation of the mono and bis adducts by fast atom bombardment tandem mass spectrometry indicated that carbamoylation of oxytocin occurred preferentially at Cys-6 and that Cys-1 and/or Tyr-2 were secondary sites of modification. Upon incubation of S-[N-([14C]methyl)carbamoyl]glutathione (14C-SMG) with native bovine serum albumin (BSA), radioactivity became bound covalently to the protein in a time- and concentration-dependent fashion. "Blocking" of the lone Cys-34 thiol group of BSA in the form of a disulfide prior to exposure of the protein to 14C-SMG failed to decrease significantly the extent or time course of this covalent binding. It is concluded that carbamate thioester conjugates of MIC are reactive, carbamoylating entities which can donate the elements of MIC to nucleophilic functionalities on peptides and proteins. Free thiols appear to be preferred sites for such carbamoylation processes, a phenomenon that may have important toxicological consequences in the pathology of tissue lesions induced by MIC and related isocyanates.
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PMID:Carbamoylation of peptides and proteins in vitro by S-(N-methylcarbamoyl)glutathione and S-(N-methylcarbamoyl)cysteine, two electrophilic S-linked conjugates of methyl isocyanate. 191 31

To examine the secretion of oxytocin (OT) and progesterone (P) from a homogeneous population of cells during luteinization, we developed a serum-free culture technique for granulosa cells, obtained from individual preovulatory bovine follicles. Granulosa cells from earlier stages of the follicle development did not have the capability to secrete OT under the in vitro conditions used. For optimal stimulation of the cells the medium (a 1:1 mixture of Dulbecco's modified Eagle's medium and Ham's F-12) was supplemented with bovine serum albumin (BSA) and insulin. OT was detectable from day 1 of culture reaching a maximum level between days 2 and 4 and then declined towards day 5. In the absence of insulin OT declined from day 1 onwards and was undetectable from day 4. When cells were cocultured with theca tissue or theca-conditioned medium (TCM), there was an enhancement in OT secretion, but not in P secretion. Other tissues including liver, kidney, aorta, muscle and adrenal incubated with the cells induced a similar increase in OT production. In the presence of insulin progesterone secretion was increased and was correlated with OT production, but did not show a consistent pattern among follicles. We conclude that (a) culture of granulosa cells from an individual follicle in a serum-free medium can be used to study the secretion of OT and P from bovine granulosa cells, (b) insulin is essential for the optimal production of OT and P by these cells, and (c) the addition of theca or other tissues enhanced OT secretion by a mechanism not understood.
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PMID:Oxytocin and progesterone secretion by bovine granulosa cells of individual preovulatory follicles cultured in serum-free medium. 218 57

To determine the effects of relaxin, oxytocin, and prostaglandin F2 alpha on progesterone secretion, bovine luteal cells from different stages of gestation were dispersed in Medium 199 with 200 units/ml penicillin, 1.0% kanamycin, 0.5% bovine serum albumin, and 400 units/ml collagenase. Cells (10(5) were cultured in 400 microliters of Dulbecco's modified Eagle's medium and Ham's F-12 medium containing fetal bovine serum and antibiotics, in Falcon multiwell plates, in a humidified environment of 95% O2 and 5% CO2 at 37 degrees C. Cells were cultured for 24 hr without treatment and thereafter with medium-hormone replacement every 24 hr. Progesterone was quantified from unextracted media by radioimmunoassay. Basal progesterone secretion after 24 hr was 1.81 +/- 0.14, 1.76 +/- 0.17, 0.54 +/- 0.49, and 0.57 +/- 0.21 pg/ml per viable luteal cell from 145-, 165-, 185-, and 240-day-old corpora lutea, respectively. Basal progesterone secretion increased (P less than 0.05) with time in culture. Relaxin induced a dose-dependent (greater than 100 ng/ml) increase in progesterone release, compared with the controls. Oxytocin and prostaglandin F2 alpha induced greater release (P less than 0.05) of progesterone than relaxin at all stages of gestation, but progesterone release was dependent on the stage of gestation and the duration in culture. Luteinizing hormone (100 ng/ml) stimulated whereas 17 beta-estradiol (50 ng/ml) inhibited progesterone secretion by luteal cells at all stages of gestation examined. Relaxin obliterated the prostaglandin- and oxytocin-induced progesterone secretion by bovine luteal cells from 145 to 214 days of gestation. Thus, relaxin, cloprostenol, and oxytocin regulate progesterone production by cultured bovine luteal cells, but hormone secretion was dependent on the stage of gestation.
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PMID:Relaxin, oxytocin, and prostaglandin effects on progesterone secretion from bovine luteal cells during different stages of gestation. 223 7

Endopeptidase-2, the second endopeptidase in rat kidney brush border [Kenny & Ingram (1987) Biochem. J. 245, 515-524] has been further characterized in regard to its specificity and its contribution to the hydrolysis of peptides by microvillar membrane preparations. The peptide products were identified, after incubating luliberin, substance P, bradykinin and angiotensins I, II and III with the purified enzyme. The bonds hydrolysed were those involving a hydrophobic amino acid residue, but this residue could be located at either the P1 or P1' site. Luliberin was hydrolysed faster than other peptides tested, followed by substance P and bradykinin. Human alpha-atrial natriuretic peptide and the angiotensins were only slowly attacked. Oxytocin and [Arg8]vasopressin were not hydrolysed. No peptide fragments were detected on prolonged incubation with insulin, cytochrome c, ovalbumin and serum albumin. In comparison with pig endopeptidase-24.11 the rates for the susceptible peptides were, with the exception of luliberin, much lower for endopeptidase-2. Indeed, for bradykinin and substance P the ratio kcat./Km was two orders of magnitude lower. Since both endopeptidases are present in rat kidney microvilli, an assessment was made of the relative contributions to the hydrolysis of luliberin, bradykinin and substance P. Only for the first named was endopeptidase-2 the dominant enzyme; for bradykinin it made an equal, and for substance P a minor, contribution.
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PMID:The metabolism of neuropeptides. Hydrolysis of peptides by the phosphoramidon-insensitive rat kidney enzyme 'endopeptidase-2' and by rat microvillar membranes. 246 6

A competitive, double antibody enzyme immunoassay for oxytocin in a heterologous system was developed. Horseradish peroxidase was conjugated with oxytocin using N-succinimidyl 3-(2-pyridyldithio) propionate, and rabbit anti-oxytocin serum was produced by immunization of oxytocin-bovine serum albumin complex which was prepared by the carbodiimide method. The sensitivity of the assay was 4 microIU/tube, which corresponded to 10 microIU per ml using 400 microliters of the sample which was extracted from the same volume of plasma by means of SEP-PAK C18 cartridges. The coefficients of variation for different levels of oxytocin ranged from 6.8-15.9% and 8.5-16.7%, for intra- and inter-assay. Recovery of oxytocin added to plasma after extraction was 99-117%. No or little cross-reaction with arginine- and lysine-vasopressin was found. Plasma oxytocin concentrations determined by the proposed enzyme immunoassay were well correlated with those determined by radioimmunoassay (r = 0.90).
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PMID:Enzyme immunoassay for oxytocin. 269 18

Six dairy cows were treated before milkings with either oxytocin (Pitocin, 20 i.u.) or ACTH (Synacthen, 150 i.u.), principally to determine their effect on the ratio of citrate: lactoferrin concentrations in the milk. With ACTH treatment, after 3 d milk yield and citrate concentration decreased significantly, lactoferrin and bovine serum albumin (BSA) concentrations increased significantly. Somatic cell counts (SCC) increased temporarily in the milk of three of the cows which previously had greater than 100 000 cells/ml. Lactoferrin yield remained fairly constant but citrate yield was significantly reduced. The citrate: lactoferrin molar ratio decreased from 1373 to 606. With oxytocin treatment, after 4 d milk yield first increased and then significantly decreased, citrate concentration decreased significantly while there were no significant changes in lactoferrin or BSA concentration or in the yield of any other milk constituents. The citrate: lactoferrin molar ratio decreased from 1621 to 1301. There were no significant changes in SCC either during treatment or 4 d after treatment but there was a significant rise at 16 d after treatment. It was concluded that in lactating cows both hormones affected citrate and lactoferrin concentrations in the direction that would improve the antibacterial properties of milk, but that this was accompanied by adverse effects on milk secretion. The extent of the change was not sufficient to be likely to produce inhibition of coliform bacteria.
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PMID:Effect of ACTH and oxytocin treatment on lactoferrin and citrate in cows' milk. 299 89

The binding sites for [125I]LHRH were characterized in membranes from the hypthalamus and the effect of estrogen on the binding characteristics was studied in ovariectomized female rats. The radioligand, [125I]LHRH, was found to bind specifically to membranes from the hypothalamus at a maximal level, with an optimal temperature of 0 degrees C and a pH between 7 and 8. The binding was enhanced by NaCl at a concentration of 0.1-0.2 M. The specifically bound [125I]LHRH was only displaced by LHRH, but not by sodium iodide (NaI), bovine serum albumin and other hormones, such as thyrotropin-releasing hormone, bradykinin, oxytocin, prolactin, luteinizing hormone and growth hormone. The divalent metal ions, copper (Cu2+) and mercury (Hg2+), inhibited the specific binding of [125I]LHRH completely, whereas magnesium (Mg2+) and calcium (Ca2+) caused a decrease in binding. As revealed from Scatchard plot analysis, the binding sites for [125I]LHRH in the hypothalamus had a dissociation constant of 0.40 +/- 0.03 microM and the maximum number of binding sites was 98.55 +/- 4.34 pmol/mg protein. Treatment of female rates (ovariectomized for 3 weeks) with 4 micrograms of estradiol benzoate caused a statistically significant decrease in the maximal number of binding sites without any significant effect on the dissociation constant. However, the direct addition of estradiol hemisuccinate to the membrane preparations had no statistically significant effect on the specific binding of [125I]LHRH. The present study provides the evidence that estrogen decreases the density of binding sites for [125I]LHRH in the hypothalamus in vivo.
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PMID:The effect of estrogen on luteinizing hormone-releasing hormone binding sites in hypothalamic membranes. 331 92


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