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)

The secretory pattern of oxytocin was determined in blood samples taken at 1-minute intervals for 30 minutes from 32 parturient women. The samples were collected in a manner that minimized degradation by plasma oxytocinase, and a highly specific antibody was used for the radioimmunoassay. The results indicated that oxytocin is secreted in discrete pulses of short duration. The frequency of the pulses was significantly higher during spontaneous labor than before the onset of labor. The mean pulse frequencies per 30 minutes were 1.2 +/- 0.54 before labor, 4.2 +/- 0.45 during the first stage, and 6.7 +/- 0.49 during the second and third stages of labor. The mean pulse durations in these three groups were 1.2 +/- 0.20, 1.9 +/- 0.28, and 2.0 +/- 0.26 minutes, respectively. The amplitude of the pulses was variable with no significant differences between the groups, the majority being around 1.0 microU/ml. The spontaneous pulses were of similar magnitude as those measured in 18 women after intravenous injections of 4 to 16 mU of oxytocin, which doses stimulated uterine contractions. We therefore conclude that the pulses of oxytocin observed at increasing frequency during spontaneous labor are of physiologic significance and provide evidence for the participation of oxytocin in the onset and maintenance of spontaneous labor.
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PMID:Oxytocin secretion and human parturition: pulse frequency and duration increase during spontaneous labor in women. 195 88

Oxytocin (OT) binds to specific receptors of myometrial cells, inducing and increasing myometrial contractions. During pregnancy and especially close to term, an increase in the myometrial OT-receptor concentration is found, leading to an increased sensitivity of the myometrium towards circulating OT. The factors determining the receptor level are not completely understood, but may include the level of steroids, OT- and oestrogenreceptors. Because of the increased sensitivity, only a small increase in the maternal OT blood-level is necessary to induce myometrial contractions at term. The level of maternal plasma OT does not change significantly throughout pregnancy. The fetus is found to secrete considerable amounts of OT during the first stage of labour, which reaches the myometrium in spite of the high level of oxytocinase in placenta. At the second stage of labour the distension of the lower birth canal might cause release of OT from the maternal neurohypophysis into the blood, increasing the myometrial contractions. This mechanism is observed in animals, but not established in the human.
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PMID:Oxytocin and the initiation of parturition. A review. 217 95

The metabolic clearance rate (MCR) of oxytocin (OT) was determined by use of constant infusion techniques to achieve low and high plasma OT concentrations in 10 women in late pregnancy and again 8-10 wk postpartum (mean plasma oxytocinase activity was 2.1 IU/ml plasma at term and less than 0.1 IU/ml plasma 8-10 wk postpartum). At the lower plasma OT concentrations (5.0 and 5.2 pg/ml, pregnant and postpartum, respectively) produced by infusion of 17.9 ng/min in pregnancy and 4.3 ng/min postpartum, mean MCR of OT was increased fourfold during pregnancy (5.7 +/- 0.6 and 1.3 +/- 0.1 l/min, pregnant and postpartum, respectively; P less than 0.001). At the higher plasma OT concentrations (8.0 and 8.0 pg/ml, pregnant and postpartum, respectively) produced by infusion of 35.7 ng/min in pregnancy and 8.5 ng/min postpartum, mean MCR of OT was likewise markedly increased during pregnancy compared with postpartum values (7.1 +/- 1.9 and 1.4 +/- 0.1 l/min, respectively; P less than 0.01). The MCR of OT was independent of plasma concentration (between 5 and 8 pg/ml) during pregnancy and in the postpartum period. It is concluded that the MCR of OT is increased markedly during human pregnancy. This may be due to concomitant increases in in vivo cystine aminopeptidase activity or other less specific pregnancy-associated metabolic changes.
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PMID:Effect of human pregnancy on metabolic clearance rate of oxytocin. 237 27

The presence of the human placental enzyme, oxytocinase, in blood samples taken during pregnancy causes major methological problems in the radioimmunoassay for plasma oxytocin. Inadequate inhibition of the enzyme activity may lead to spuriously high or low values of plasma oxytocin. This study systematically investigates a variety of enzyme inhibitors. The optimum inhibitory system was obtained by the addition of 10 microliters of cold 125 mmol/l 1.10 phenanthrolene and 1 mol/l EDTA per ml of whole blood into the syringe. Complete enzyme inhibition was maintained for up to 60 min, during which time the lithium heparinized plasma samples were extracted by the Florisil method. Following extraction there was no enzyme activity in the extract residue. Concentrations of phenanthrolene and EDTA necessary to eliminate enzyme activity were 50- and 10-fold greater, respectively, than in any previously reported method. Recovery of synthetic oxytocin added to pregnancy plasma with inhibitors was 80% or higher, over the concentration range 1-100 pmol/l. Extract residue could be stored at -20 degrees C for up to 7 weeks. Dilutions of pregnancy plasma extracts ran parallel to the oxytocin standard curve. Studies on plasma concentrations of oxytocin (OT) during the first stage of labour in 6 patients showed that 3 had pulsatile plasma OT, peak values ranging from 4-10 pmol/l in phase with uterine concentrations, but 2 who had regular uterine activity had no episodic changes in plasma OT. One patient with hypocontractile labour had low non-fluctuating plasma OT.
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PMID:Evaluation of enzyme inhibitors of pregnancy associated oxytocinase: application to the measurement of plasma immunoreactive oxytocin during human labour. 243 27

An aminopeptidase from monkey (Macaca radiata) liver, inactivating oxytocin in vitro and located predominantly in the lysosomal and microsomal fractions, was purified by chromatography on Bio-Gel HTP, DEAE-Sephacel and nickel ion chelate gel and gel filtration on Sephacryl S300. Absence of binding to nickel ion chelate gel indicated the absence of exposed histidine and thiol residues on the enzyme. The enzyme appeared to be a high molecular weight (Mr 106,000) monomeric protein. It was sensitive to inhibition by metal chelators and was found to be a zinc metalloprotein by atomic absorption spectrophotometry. Divalent metal ions Ni2+ and Co2+, and sulphydryl activators glutathione and 2-mercaptoethanol had activating effects, while 4-chloro mercuribenzoate, amino acids with large hydrophobic side chains and L-cystine, beta-lactam antibiotic cloxacillin and peptidase inhibitor amastatin had inhibitory effects on the enzyme activity. The enzyme was most active against S-benzyl L-cysteine 4-nitroanilide substrate. The properties of the enzyme were distinct from those of the well-characterized alanine and leucine aminopeptidases (EC 3.4.11.2 and EC 3.4.11.1 respectively) of liver, and of primate placental cystine aminopeptidases (EC 3.4.11.3).
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PMID:A peptidase activity from primate liver that inactivates oxytocin in vitro: purification and partial characterization. 275 77

A technique for complete oxytocinase inhibition has been combined with a rapid serial sampling strategy to determine the plasma oxytocin concentration in eight women undergoing amniotomy for the induction of labour at term and in eight control women. Amniotomy was not associated with an increase in plasma oxytocin concentration. Furthermore, the concentrations were not increased for 20 min following the procedure. Labour was not established in any patient by the end of the 30-min study period.
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PMID:Amniotomy-induced labour is not mediated by endogenous oxytocin. 277 93

Acid-base balance, lactate dehydrogenase, creatine phosphokinase, hydroxybutyrate dehydrogenase, oxytocinase and the final products of peroxide oxygenation of lipids-malonate dialdehyde and antioxidant activity were studied on 60 parturients, divided into two groups as each group had 30 women. Hyperbaric oxygen treatment in combination with oxytocin was studied on uterine inertia. The control group consisted of 20 parturients with normal course of delivery.
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PMID:[Dynamic biochemical indices of parturients with uterine inertia against a background of hyperbaric oxygen and drug treatment]. 280 77

L-cystine aminopeptidase (CAP) activity in plasma was determined by spectrophotometry in 243 normal pregnant women in week 20-40 and 68 pregnant women with premature pains in week 28-37 of pregnancy. For significantly diminished CAP activity, pains and the subsequent premature birth correlated with infantile dystrophy, while in case of normal CAP activity the number of premature births was significantly less and newborns had eutrophic birth weights. In addition, radioimmunological measurements of oxytocin concentration in plasma were performed in ten pregnant women each of these groups. In women with premature pains, the oxytocin concentration was significantly higher than in normals. The present findings suggest that fetal oxytocin release might be the trigger signal for pains, thus causing premature birth. This signal might be chronically induced by a stress situation which manifests itself in hypotrophy of the newborns.
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PMID:[Cystine aminopeptidase and oxytocin in the plasma of pregnant patients with premature labor]. 407 76

Aminopeptidase from dysgerminoma was purified and characterized using L-leucine-beta-naphthylamide as substrate. The enzyme was resistant to puromycin, methionine, amastatin, bastatin, and EDTA, and it was heat labile at 60 degrees C. The enzyme showed the same electrophoretic mobility as pregnant-patient serum oxytocinase CAP1 on polyacrylamide gel electrophoresis. Km value against S-benzylcysteine-p-nitroanilide was 4.2 X 10(-4) M. Oxytocin and vasopressin competitively inhibited the enzyme activity. Molecular weight of the enzyme was estimated to be 80,000 by Sephadex G-200 column chromatography. These results suggest that aminopeptidase from dysgerminoma is an oxytocinase-like enzyme, a placenta-specific protein.
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PMID:Oxytocinase-like enzyme in an ovarian dysgerminoma: a placenta-specific protein. 408 42

To detect antigens in the plasma of pregnant women that were not found in nonpregnant untreated normal women or males, highly sensitive immunodiffusion techniques with hyperimmune rabbit antiserum were used. The number of pregnancy-associated plasma constituents increased as pregnancy progressed in the 165 patients studied, with all 4 constituents usually seen in the third trimester. The 60 males and 111 nonpregnant women studied did not show any of these antigens. There were significant differences between second and third trimester reactions. (p less than .001). None of the antigens represented human chorionic gonadotropin, human placental lactogen, oxytocin, C-reactive protein, oxytocinase, alkaline phosphatase, or esterase. One of these constituents is present during combined estrogen-progesterone therapy.
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PMID:Antigenic constituents in pregnancy plasma which are undetectable in normal non-pregnant female or male plasma. 462 19


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