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

Serum oxytocic and oxytocinase activities were examined in 50 females with normal pregnancy and 50 with threatened abortion by using biological (oxytocin) and biochemical (oxytocinase) methods. The findings suggest that there is no regular changes in serum oxytocic activity in the course of pregnancy, whereas its oxytocinase activity significantly increases with pregnancy development. The females with threatened abortion showed the same values of serum oxytocic activity as those with normal pregnancy, but much lower oxytocinase activity. The assay of serum oxytocinase activity may be of diagnostic value when threatened abortion is suspected.
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PMID:[Serum oxytocin and oxytocinase activities in women during pregnancy]. 186 62

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

Metabolic clearance rates (MCR) of arginine vasopressin (AVP) were measured serially in five women starting before conception, during gestational weeks 7-8 (early), 22-24 (middle), and 36-38 (late pregnancy), and again 10-12 wk postpartum. Hormonal disposal rates were determined after water loading to suppress endogenous AVP release using a constant infusion method designed to achieve three different steady-state concentrations of plasma AVP (PAVP) on each test occasion. Dose schedules were altered in mid- and late pregnancy to obtain comparable AVP levels at each stage of the protocol. Prehydration decreased plasma osmolality sufficiently to suppress AVP release, as circulating AVP-neurophysin measured serially in three of the women was undetectable. The MCR of AVP was similar before conception (0.75 +/- 0.31, 0.79 +/- 0.34, and 0.76 +/- 0.28 liters/min at PAVP of 2.6 +/- 1.9, 4.7 +/- 2.4, and 8.3 +/- 3.9 pg/ml), in early pregnancy (0.89 +/- 0.34, 0.97 +/- 0.04, and 0.95 +/- 0.40 liters/min at PAVP of 2.2 +/- 2.1, 3.9 +/- 3.2, and 7.9 +/- 3.4 pg/ml), and postpartum (0.70 +/- 0.21, 0.69 +/- 0.24, and 0.75 +/- 0.20 liters/min at PAVP 3.5 +/- 1.8, 5.1 +/- 3.7, and 9.1 +/- 4.2 pg/ml). Values at mid-pregnancy (2.8 +/- 1.3, 3.0 +/- 1.2, and 2.7 +/- 1.2 liters/min at PAVP 2.3 +/- 2.2, 4.0 +/- 3.6, and 7.7 +/- 3.9 pg/ml) and late pregnancy (3.2 +/- 1.4, 3.3 +/- 1.4, and 2.9 +/- 1.2 liters/min at PAVP 1.9 +/- 2.0, 3.8 +/- 2.6, and 7.4 +/- 4.1 pg/ml) increased 3-4-fold (all P less than 0.01). Plasma vasopressinase, undetectable at 7-8 gestational wk, increased markedly by mid- and slightly more by late gestation. Finally, relationships between PAVP and urine osmolality were similar before, during, and after pregnancy. We conclude that marked increments in the MCR of AVP occur between gestational weeks 7 and 8 and mid-pregnancy, which parallel the period of greatest rise in both trophoblastic mass and plasma vasopressinase. There was no evidence of a renal resistance to AVP during gestation.
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PMID:Changes in the metabolic clearance of vasopressin and in plasma vasopressinase throughout human pregnancy. 270 33

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

The degradation of oxytocin (formula; see text) by human placental particulate and soluble fractions, pregnant and non-pregnant sera, and purified enzymes such as microsomal placental leucine aminopeptidase (P-LAP), retroplacental serum P-LAP and placental post-proline endopeptidase, was studied by measuring liberated amino acids with a high performance liquid chromatograph (HPLC). While the placental particulate fraction degraded oxytocin almost completely into single amino acid and amide, the placental soluble fraction did not liberate any amino acid and amide. Purified retroplacental P-LAP liberated Tyr2, Ile3, Gln4 and Asn5 from the cyclic structure of oxytocin actively. Pregnancy serum containing the retroplacental P-LAP liberated also these amino acids and amides. Purified microsomal P-LAP liberated Leu8 in addition to these amino acids and amides. Although purified placental post-proline endopeptidase or porcine kidney leucine aminopeptidase (LAP) could not liberate any amino acid and amide from oxytocin, the combination of the post-proline endopeptidase with porcine kidney LAP or with placental microsomal P-LAP actively liberated all amino acids and amides detectable by HPLC. When the ratio of amino acid liberation velocity to LAP activity measured with leu-p-nitroanilide was calculated, the ratios for cyclic amino acids such as Tyr2 and Ile3 were high with the placental particulate fraction, the mixture of post-proline endopeptidase and microsomal P-LAP, retroplacental P-LAP, and pregnancy serum. The ratio for Leu8 was high with the placental particulate fraction and the mixture of post-proline endopeptidase and microsomal P-LAP.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:In vitro degradation of oxytocin by pregnancy serum, placental subcellular fractions and purified placental aminopeptidases. 391

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


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