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)

Synthetic oxytocin (OT) was infused iv in four men at 3 mU/min, and the rate was doubled every 90 min for a total of three infusion periods. The mean (+/- SEM) OT MCR was 16.4 +/- 1.7 ml/kg X min and was independent of the rate of infusion. A method for measuring OT in urine was developed using an octadecasilyl-silica column for extraction of the hormone. The extracted residue was reconstituted in potassium phosphate buffer, pH 7.4, for RIA. The minimum detectable level of OT in urine was 0.2 microU/ml (defined as a bound to free ratio of approximately 90%). The mean recovery of OT was 77 +/- 2%. The mean (+/- SEM) concentration of endogenous OT in urine was 10.2 +/- 1.4 microU/ml. Endogenous OT in urine eluted from a reverse phase high pressure liquid chromatography column as a single peak of OT immunoreactivity in the position of synthetic OT. Urinary OT excretion during infusion of synthetic OT was linearly correlated with plasma OT concentration whether calculated as microunits of urinary OT per mg creatinine (r = 0.89) or urinary OT per min (r = 0.93). Mean urinary fractional clearance of OT (OT clearance/creatinine clearance) was 3.6% renal clearance of OT (5.5 ml/min or 0.43% of MCR). Thus, OT MCR was constant over a wide range of physiological plasma OT levels and was similar to MCR in pregnant women studied previously in this laboratory. Less than 1% of OT was cleared in urine. This study defines the relationship between urinary and plasma OT during steady state infusion of physiological concentrations of the hormone and indicates that measurements of OT in urine by RIA may prove helpful for pharmacokinetic and physiological studies of OT-related events in humans.
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PMID:Clearance studies of oxytocin in humans using radioimmunoassay measurements of the hormone in plasma and urine. 379 53

Oxytocin (OT) was measured by RIA in plasma of women during hypocontractile labor before and during graded doses of iv infused synthetic OT. Based upon in vitro studies of recovery of OT from pregnancy plasma, blood was collected into heparinized tubes which were kept at 4 C. The addition of EDTA and phenanthrolene to an aliquot of each sample resulted in measured levels of OT in plasma that correlated closely with levels measured in the absence of these reagents (r2 = 0.86). Comparison of OT levels in plasma of normal individuals determined in the presence and absence of these reagents also yielded a high degree of linear correlation (r2 = 0.97). The mean level of OT in 11 women during hypocontractile labor before the infusion of OT was 1.01 +/- 0.31 (+/- SEM) microU/ml. There was a linear correlation between the dose of OT infused and the level of OT in plasma with infused doses of OT between 1 and 4 mU/min (r2 = 0.99). The time of onset of adequate uterine contractility was recorded by on-line computer analysis, and the level of OT in plasma obtained simultaneously was variable among the women. The mean OT MCR in these women was 17.4 +/- 9.2 (+/- SEM) ml/kg X min, similar to the MCR in normal men (17.6 +/- 2.1 ml/kg X min). Levels and pharmacokinetics of OT during hypocontractile labor were similar to those in nonpregnant individuals and women in late pregnancy. The variability in OT concentrations at the time of adequate uterine contractility suggests that individual myometrial sensitivity is an important determinant of the response to administered OT in humans.
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PMID:Studies of oxytocin in plasma of women during hypocontractile labor. 669 37

The MCR and placental permeability to oxytocin were determined in chronically catheterized pregnant sheep. Simultaneous maternal and fetal plasma oxytocin (OT) concentrations were measured by RIA before and during continuous infusion of synthetic OT to steady state conditions. Baseline fetal plasma OT concentrations were significantly higher than simultaneously collected maternal concentrations (1.6 +/- 0.13 vs. 1.1 +/- 0.13 muU/ml, respectively; P less than 0.01). Mean fetal OT MCRs were 12.0 +/- 1.35 and 12.1 +/- 1.09 ml/kg . min at OT infusion rates of 64 and 640 muU/kg . min. Mean maternal MCRs were 12.1 +/- 2.64 and 12.4 +/- 1.38 ml/kg . min at OT infusion rates of 80 and 800 muU/kg . min. Uterine contractions were induced by maternal OT infusion of 800 muU/kg . min but not by lower infusion rates; no uterine contractions were induced by fetal OT infusion. OT did not appear to cross the placenta in either direction under the present study conditions.
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PMID:Metabolic clearance rate and transplacental passage of oxytocin in the pregnant ewe and fetus. 735 32

Plasma oxytocin (OT), FSH, and LH were measured by specific RIA in eight healthy adult males before, during, and after stopping iv infusions of OT. With a constant infusion of 132 mU OT/min for 60 min, plasma OT reached a steady state concentration of 228-241 pg/ml at 30-60 min. When the dose of oxytocin infused was doubled every 15 min, plasma OT increased from 81.0 +/- 17.9 pg/ml (mean +/- SE) with 32 mU/min to reach a steady state concentration of 378 +/- 73.4 pg/ml with 256 mU/min (1 muU = 2 pg OT). The curve of disappearance of plasma OT could be resolved into a single exponential curve in all of the subjects, with a mean calculated half-life of 10.3 +/- 1.6 min (range, 5.3-17.3 min). The mean MCR of OT was 21.5 +/- 3.3 ml/kg.min, and the mean apparent volume of distribution was 305 +/- 46 ml/kg. Plasma FSH and LH showed no significant change throughout OT infusion and for up to 60 min after stopping the OT infusion. The findings demonstrate that in man 1) plasma OT concentration achieved is closely related to the infusion rate, 2) OT infusion does not affect plasma FSH and LH, and 3) the apparent volume of distribution of OT suggests that infused OT is distributed into space or spaces other than the circulating plasma volume.
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PMID:Oxytocin levels and disappearance rate and plasma follicle-stimulating hormone and luteinizing hormone after oxytocin infusion in men. 735 23

Angus x Hereford multiparous cows were assigned to four treatments: 1) mastectomized+calf weaned at birth (MCW; n = 7); 2) mastectomized+calf presence restricted to noninguinal contact (MCR; n = 7); 3) mastectomized+unrestricted calf presence (MCP; n = 7); and 4) udder-intact cows+unrestricted calf presence (UICP; n = 8). Except for MCW cows, cow-calf pairs were penned together individually from parturition (d 0) until d 35 when calves were weaned. On d 7, calves in MCP and UICP treatments were separated overnight from their dams, and before and upon reunion, blood samples were collected from the cows to assess changes in oxytocin, cortisol, and prolactin. Calves in the MCP and UICP treatments attempted to or suckled their dams for a similar duration upon reunion, respectively. Concentrations of cortisol and percentage of change in oxytoxin and prolactin were increased (P < .05) for up to 12 min in MCP cows after reunion with their calves. Average concentrations of serum LH in samples collected on d 14, 21, 28, and 35 did not differ in noncyclic cows among treatments within day postpartum (except for greater [P < .05] LH in MCW cows on d 21). However, MCP cows had more (P < .05) LH pulses (d 21), greater (P < .05) variability in LH pulses (d 21), greater (P < .05) variability in LH concentrations, and greater (P < .05) average maximum concentrations of LH than UICP cows after d 14. Intervals to first ovulation were similar in MCW and MCR cows but shorter (P < .01) than those in MCP and UICP cows. Attempted suckling of mastectomized dams by their calves was associated with increased serum cortisol and percentage of increase in serum oxytocin and prolactin. Despite increased LH in MCP cows, intervals to first ovulation did not differ from those of UICP cows.
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PMID:Estrus, ovulation, luteinizing hormone, and suckling-induced hormones in mastectomized cows with and without unrestricted presence of the calf. 818 86

The central melanocortin (MC) system has been widely studied for its effects on food intake and sexual behavior. However, the MC system, and more specifically the MC4 receptor (MC4R), also interacts with neurochemical systems that regulate socioemotional behaviors, including oxytocin (OT) and dopamine. In monogamous prairie voles, OT and dopamine interact to promote partner preference formation, a laboratory measure of an enduring social bond between mates. Here we investigated the effects of MC receptor activation on partner preference formation in prairie voles, as well as the interaction between the MC and OT systems during this process. Peripheral administration of the brain penetrant MC3/4R receptor peptide agonist, Melanotan II (MTII), and the highly selective, small-molecule MC4R agonist, Pf-446687, enhanced partner preference formation in the prairie vole, but not in the non-monogamous meadow vole. MTII-induced partner preferences were enduring, as they were present 1 week after drug manipulation. The prosocial effects of MCR agonists may be mediated, in part, through modulation of OT, as coadministration of an OT receptor antagonist prevented MTII-induced partner preferences. MTII also selectively activated hypothalamic OT neurons and potentiated central OT release. As OT has been shown to enhance some aspects of social cognition in humans, our data suggest that the MC4R may be a viable therapeutic target for enhancing social function in psychiatric disorders, including autism spectrum disorders and schizophrenia, potentially through activation of the OT system.
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PMID:Melanocortin Receptor Agonists Facilitate Oxytocin-Dependent Partner Preference Formation in the Prairie Vole. 2565 47