UNIPROT:P01178 - FACTA Search

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

Pulsatile release of uterine prostaglandin F2alpha (PGF2alpha) induces luteolysis in ruminants. However, the mechanism(s) that initiates and maintains luteolysis has not been defined. The present study tested the hypothesis that the endogenous PGF2alpha pulse generator is uterine-derived platelet-activating factor (PAF). Ovariectomized ewes were given exogenous progesterone (P), estradiol (E), or both (P+E, mimicking the normal luteal phase). Only ewes treated with steroids released PAF into the uterine lumen and had increased PAF:acetylhydrolase activity in the uterine lumen. Steroid treatment also influenced the capacity of the uterus to release PGF2alpha in response to exogenous PAF. PAF infusion did not affect plasma PGF2alpha metabolite (PGFM) levels in control (no steroid treatment) ewes but increased plasma PGFM levels in P+E ewes (P < 0.001) and ewes treated with P or E alone (P < 0.05). Infusion of PAF followed by or coincident with oxytocin (OT) acted in a synergistic manner to increase plasma PGFM levels. Repeated infusion of PAF into the uterus at 1-h intervals induced tachyphylaxis of the PGFM response to PAF; however, sensitivity of the uterus to PAF returned spontaneously by the 6th h. Interferon-tau (IFN-tau) inhibits pulsatile release of PGF2alpha during pregnancy to prevent luteolysis. Exogenous recombinant ovine IFN-tau (50 microgram) inhibited the uterine response to PAF alone or the combined effects of PAF and OT. These results indicate that uterine PAF fulfills many of the criteria for an endogenous PGF2alpha pulse-generator: steroid induction of PAF production and uterine responsiveness to PAF-induced release of PGF; synergistic stimulation of PAF-induced PGF release by OT; inhibition of PAF effects by IFN-tau; and PAF's ability to induce pulses of PGF with a periodicity during a period of chronic exposure of the uterus to PAF.
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PMID:Platelet-activating factor may act as an endogenous pulse generator for sheep of luteolytic PGF2alpha release. 1019 17

Interferon tau (IFNtau) is the antiluteolytic signal produced by the conceptus of ruminants. Intrauterine administration of recombinant ovine IFNtau suppresses expression of endometrial estrogen receptor (ER) and oxytocin receptor (OTR) in the luminal and superficial glandular epithelia to abrogate the production of luteolytic prostaglandin F(2alpha) (PGF(2alpha)) pulses. Subcutaneous (s.c.) injections of recombinant ovine (o) IFNtau appear to extend the interestrous interval by altering uterine PGF(2alpha) response to oxytocin. The present study tested the hypothesis that antiluteolytic effects of roIFNtau injected into the uterine lumen (paracrine) or s.c. (endocrine) are equivalent in suppressing expression of endometrial ER and OTR and inducing uterine expression of type I IFN-regulated Mx and ubiquitin cross-reactive proteins (UCRP). Sixteen cyclic ewes were fitted with uterine catheters on Day 5 (Day 0 = estrus), were assigned randomly to receive treatment with control proteins or roIFNtau (2 x 10(7) antiviral units/day) by either intrauterine or s.c. injections from Days 11 to 15, and were ovariohysterectomized on Day 16. Results indicated that expression of ER and OTR mRNAs in endometrial epithelium was suppressed by intrauterine but not by s.c. injections of roIFNtau. Intrauterine injections of roIFNtau increased expression of Mx and UCRP mRNA in the endometrium. Subcutaneous injections of roIFNtau increased endometrial Mx mRNA levels but not UCRP mRNA. Unexpectedly, intrauterine and s.c. injections of roIFNtau were equally effective in inducing expression of Mx and UCRP mRNA in the corpus luteum. Although s.c. injections of roIFNtau induced Mx mRNA in the endometrial epithelium, s.c. injections of roIFNtau did not abrogate activation of the uterine luteolytic mechanism by suppressing epithelial ER and OTR expression. Therefore, results of this study failed to support the assumption that endocrine roIFNtau mimics antiluteolytic effects of paracrine IFNtau to improve pregnancy rates in sheep.
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PMID:Differential effects of intrauterine and subcutaneous administration of recombinant ovine interferon tau on the endometrium of cyclic ewes. 1041 28

Effects of lipid infusion into postpartum (PP) beef heifers on plasma concentrations of linoleic acid and prostaglandin (PG) F(2alpha) metabolite (PGFM), days to first estrus, and subsequent pregnancy rate were examined. Treatments (n = 5 per group) of 1 L intralipid (20% soybean oil; IL), 1 L 50% dextrose (DEXT; isocaloric to IL), 0.5 L intralipid (0.5 IL), and 1 L physiological saline (SAL) were infused i.v. over 4 h on each of Days 7 through 11 PP. Capacity of the uterus to produce PG was evaluated after i.v. injection of 150 IU of oxytocin (OT) to IL- and DEXT-treated heifers Day 12 PP. Change in plasma concentrations of PGFM from 0 to 4 h was greater for IL-treated heifers than for heifers given other treatments on Day 7 (P = 0.04) and on Day 11 (P = 0.01), but not on Day 9 (P>0.10). Plasma linoleic acid on Day 11 and OT-induced release of PGFM on Day 12 were greater in IL-treated heifers compared with DEXT-treated heifers (P<0.06 and P = 0.01, respectively). There were no significant differences among treatments for mean days to first estrus or pregnancy rate. Infusion of lipid increased systemic concentrations of linoleic acid and increased the capacity of PP heifers to produce uterine PGF(2alpha) as indicated by plasma PGFM concentration after OT injection.
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PMID:Prostaglandin f(2alpha) concentrations, fatty acid profiles, and fertility in lipid-infused postpartum beef heifers. 1052 80

During reproductive processes, prostaglandin (PG) E(2) (PGE(2)) and PGF(2alpha) play important roles in which they often exert opposite effects. At the time of recognition of pregnancy in vivo, PGF(2alpha) is recognized as the luteolytic factor in ruminants and in most species including human, whereas PGE(2) may exert a luteoprotective action. We have previously demonstrated that recombinant interferon-tau (rIFN-tau), the embryonic signal responsible for recognition of pregnancy in ruminants, stimulated in vitro the production of PGE(2) and prostaglandin-endoperoxide synthase 2 (Ptgs2; also called cyclooxygenase-2) gene expression in both epithelial and stromal endometrial cells. Since PGE(2) is the major prostaglandin produced by stromal cells, the effect on Ptgs2 could explain the increase in PGE(2) output. At high concentrations, however, recombinant ovine (ro) IFN-tau acts on epithelial cells by changing the primary PG produced from PGF(2alpha) to PGE(2). This change in the primary PG produced could be explained by a decrease in PGF synthase (PGFS) activity or an increase in PGE synthase activity, or by modulation of a putative PGE(2)-9-ketoreductase, which converts PGE(2) into PGF(2alpha). Therefore, we have investigated the regulation of the mRNAs for PGFS and PGE(2)-9-ketoreductase (9K-PGR), two enzymes that lead to the production of PGF(2alpha). Others have described 9K-PGR activity in uterus, ovaries, kidney, and liver of different species and have established that this enzyme could possess both 9K-PGR and 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD) activity. Some have concluded that 9K-PGR and 20alpha-HSD are identical enzymes. Using primers sequences chosen from homologous nucleotide sequences of published rabbit 20alpha-HSD/9K-PGR and rat 20alpha-HSD cDNAs, a 317-base pair (bp) fragment was amplified by reverse transcription-polymerase chain reaction (RT-PCR), cloned, and sequenced. Homologies of 83% and 78% were found with rabbit and rat 20alpha-HSD, respectively. The presence of 20alpha-HSD/9K-PGR and prostaglandin F synthase (PGFS) mRNA expression was studied semiquantitatively in cultured epithelial cells using RT-PCR. Stimulation of cells with roIFN-t resulted in a biphasic response, an inhibition of PGF(2alpha) production at low dose (1 ng/ml) and a stimulation of PGE(2) at high dose (10 microg/ml). The increase of PGE(2) was accompanied by reduced 9K-PGR and PGFS mRNA gene expression. The effect of oxytocin (OT) was also studied, and the presence of OT had no effect on either 9K-PGR or PGFS gene expression. The 20alpha-HSD/9K-PGR transcript was also detected in other bovine tissues at different intensity (liver > kidney > testis > ovaries). We believe that the 9K-PGR and PGFS can be key enzymes in the regulation of specific PGs in the endometrium during the periimplantation period.
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PMID:Detection and regulation of the messenger for a putative bovine endometrial 9-keto-prostaglandin E(2) reductase: effect of oxytocin and interferon-tau. 1061 Oct 76

Thirty ovariectomized sows were used in an experiment designed to determine whether the ability of the porcine uterus to release prostaglandin (PG) F(2alpha) in response to oxytocin is regulated by progesterone (P(4)) and estradiol (E(2)). Sows were assigned to one of four treatment groups: 1) no steroids (ovariectomized controls; n = 8), 2) E(2) (n = 8), 3) P(4) (n = 7), or 4) E(2) + P(4) (n = 7). P(4) and E(2) were administered so as to mimic the normal temporal changes that occur in these hormones during the estrous cycle. A group of intact sows (n = 9) was included for comparison. All sows received an injection of oxytocin (30 IU, i.v.) on Days 12, 15, and 18 postestrus. Jugular venous blood samples were collected from 60 min before through 120 min after injection of oxytocin for quantification of 13,14-dihydro-15-keto-PGF(2alpha) (PGFM). Preinjection baseline concentrations of PGFM, the magnitude of the PGFM response above baseline, and area under the PGFM response curve (AUC) were calculated for each sow on each day and compared among treatment groups by ANOVA. Among the ovariectomized sows receiving steroid replacement, baseline concentrations of PGFM were low on Day 12 postestrus in all four groups. On Days 15 and 18, baseline concentrations remained low in the two groups that did not receive P(4) but increased in those that did. Both the magnitude of the response to oxytocin and AUC were small on Day 12 postestrus in all 4 groups. By Day 15, the magnitude of the response and AUC increased in the group that received both P(4) and E(2) but remained low in the other three groups. By Day 18, responses to oxytocin were greater in both groups that received P(4) than in those that did not. Baseline concentrations were similar in intact sows and in those that received both P(4) and E(2) on all three days examined. The magnitude of the response and the AUC were greater in the ovariectomized sows receiving P(4) and E(2) replacement than in the intact control sows on Days 15 and 18 postestrus. From these results, we conclude that P(4) and E(2) interact to control the time when the uterus begins to secrete PGF(2alpha) in response to oxytocin and the amount of PGF(2alpha) secreted.
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PMID:Effects of progesterone and estradiol on uterine secretion of prostaglandin f(2alpha)in response to oxytocin in ovariectomized sows. 1064 74

Ovine endometrial gland development is a postnatal event that can be inhibited epigenetically by chronic exposure of ewe lambs to a synthetic progestin from birth to puberty. As adults, these neonatally progestin-treated ewes lack endometrial glands and display a uterine gland knockout (UGKO) phenotype that is useful as a model for study of endometrial function. Here, objectives were to determine: 1) length of progestin exposure necessary from birth to produce the UGKO phenotype in ewes; 2) if UGKO ewes display normal estrous cycles; and 3) if UGKO ewes could establish and/or maintain pregnancy. Ewe lambs (n = 22) received a Norgestomet (Nor) implant at birth and every two weeks thereafter for 8 (Group I), 16 (Group II), or 32 (Groups III and IV) weeks. Control ewe lambs (n = 13) received no Nor treatment (Groups V and VI). Ewes in Groups I, II, III, and VI were hemihysterectomized (Hhx) at 16 weeks of age. After puberty, the remaining uterine horn in Hhx ewes was removed on either Day 9 or 15 of the estrous cycle (Day 0 = estrus). Histological analyses of uteri indicated that progestin exposure for 8, 16, or 32 weeks prevented endometrial adenogenesis and produced the UGKO phenotype in adult ewes. Three endometrial phenotypes were consistently observed in Nor-treated ewes: 1) no glands, 2) slight glandular invaginations into the stroma, and 3) limited numbers of cyst- or gland-like structures in the stroma. Overall patterns of uterine progesterone, estrogen, and oxytocin receptor expression were not different in uteri from adult cyclic control and UGKO ewes. However, receptor expression was variegated in the ruffled luminal epithelium of uteri from UGKO ewes. Intact UGKO ewes displayed altered estrous cycles with interestrous intervals of 17 to 43 days, and they responded to exogenous prostaglandin F(2 approximately ) (PGF) with luteolysis and behavioral estrus. During the estrous cycle, plasma concentrations of progesterone in intact control and UGKO ewes were not different during metestrus and diestrus, but levels did not decline in many UGKO ewes during late diestrus. Peak peripheral plasma concentrations of PGF metabolite, in response to an oxytocin challenge on Day 15, were threefold lower in UGKO compared to control ewes. Intact UGKO ewes bred repeatedly to intact rams did not display evidence of pregnancy based on results of ultrasound. Collectively, results indicate that 1) transient, progestin-induced disruption of ovine uterine development from birth alters both structural and functional integrity of the adult endometrium; 2) normal adult endometrial integrity, including uterine glands, is required to insure a luteolytic pattern of PGF production; and 3) the UGKO phenotype, characterized by the absence of endometrial glands and a compact, disorganized endometrial stroma, limits or inhibits the capacity of uterine tissues to support the establishment and/or maintenance of pregnancy.
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PMID:Ovine uterine gland knock-out model: effects of gland ablation on the estrous cycle. 1064 86

The release of luteal oxytocin during spontaneous and prostaglandin-induced luteolysis was investigated in cows. A continuous-flow microdialysis system was used in 11 cows to collect dialysates of the luteal extracellular space between Days 12 and 24 postestrus. Seven cows were untreated and were expected to exhibit spontaneous luteolysis during sampling, whereas 4 cows received prostaglandin F(2alpha) (PGF(2alpha)) systemically between Days 13 and 15 to induce luteolysis during sampling. Oxytocin was detectable in the dialysate of all cows before Day 16 postestrus and occurred as 2 or 3 discrete pulses per 12-h sampling period. For non-PGF(2alpha)-treated cows, dialysate oxytocin content began to decline spontaneously on Day 15 postestrus and was undetectable by Day 17 postestrus. Oxytocin decay curves preceded onset of serum progesterone decline by at least 72 h and were not related temporally with onset of progesterone decline within cow. Exogenous PGF(2alpha) (25 mg, i.m.) produced a 10-fold increase in dialysate oxytocin within 1 h (1.9 +/- 0.3 pg/ml to 20.8 +/- 3.0 pg/ml; P < 0. 01). Dialysate oxytocin then declined to pretreatment concentrations within 2 h and was undetectable within 8 h posttreatment. A second PGF(2alpha) injection given 20 h after the first did not result in a measurable increase in dialysate oxytocin, probably because luteolysis was underway. Although robust luteal oxytocin release was observed after treatment with a pharmacological dose of PGF(2alpha), the lack of detectable oxytocin secretion during spontaneous luteolysis suggests that the contribution of luteal oxytocin in the cow may be less than that proposed for the ewe.
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PMID:In vivo oxytocin release from microdialyzed bovine corpora lutea during spontaneous and prostaglandin-induced regression. 1068 16

Concentrations of LH, cortisol, estradiol-17beta (E(2)), prolactin and 13,14-dihydro-15-keto-prostaglandin F(2alpha) (PGFM) were determined in cows with experimentally induced clinical mastitis during early lactation. Cows free of intramammary infection (IMI) and in the luteal phase of the estrous cycle were balanced by lactation number and days in milk and assigned to either control (n=5) or treatment (n=5) groups. Treated cows were infected experimentally (day 0), in two mammary quarters, with Streptococcus uberis and developed clinical mastitis within 60 h after inoculation as evidenced by increased mastitis scores, elevated rectal temperatures, mammary swelling and isolation of S. uberis pathogen. Four days following bacterial challenge, blood samples were collected every 20 min for 8 h for determination of PGFM and LH following administration of oxytocin and GnRH, respectively. Blood samples were also collected on days 0, 4 and 7 of the experiment to determine concentrations of E(2), prolactin and cortisol. Four days after bacterial challenge, concentrations of cortisol were higher (P=0.04) in experimentally infected cows than controls. Experimentally challenged cows had increased (P=0.02) concentrations of cortisol on days 4 and 7 compared with day 0. Control cows had no significant increase in blood cortisol during the experimental period. Baseline concentrations of PGFM did not differ between groups; however, peak concentrations of PGFM following oxytocin challenge were elevated (P=0.006) in cows with clinical mastitis compared with control animals. Prolactin, E(2) and LH did not differ between cows with clinical mastitis or controls. Experimentally induced mastitis during early lactation elevated concentrations of cortisol during the luteal phase of the estrous cycle. Furthermore, mastitic cows demonstrated an increased PGFM response following oxytocin administration. Altered reproductive efficiency in cows with clinical mastitis caused by Gram-positive pathogens may be the result of increased uterine sensitivity to prostaglandin F(2alpha) (PGF(2alpha)).
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PMID:Endocrine profiles of dairy cows following experimentally induced clinical mastitis during early lactation. 1070 98

In swine, endometrial prostaglandin F(2alpha) (PGF(2alpha)) is the luteolysin. The capacity of luminal epithelial cells isolated from the endometrium of day 16 cyclic pigs, to secrete PGF(2alpha)500 Omega/cm(2)), they were treated on the apical, basal or both surfaces with 0 or 100 nM oxytocin (OT) in Experiment 1 or phorbol 12-myristate 13-acetate (PMA) in Experiment 2. In the absence of OT or PMA, PGF(2alpha) secretion occurred primarily from the basal surface and was approximately 12-fold greater (P < 0.001) than from the apical surface. Treatment with OT did not stimulate PGF(2alpha) secretion from either surface regardless of which surface was treated. In contrast, PMA increased PGF(2alpha) secretion from both surfaces. Treatment of the apical surface or both surfaces with PMA increased (P < 0.001) PGF(2alpha) secretion similarly from both surfaces. Treatment of only the basal surface with PMA increased (P < 0.01) PGF(2alpha) secretion from both surfaces, but tended (P = 0. 06) to increase its secretion from the basal surface more than from the apical surface. These results indicated that PGF(2alpha) secretion by luminal epithelial cells obtained from cyclic pigs occurs primarily toward a basal direction and is not stimulated by oxytocin. Activation of protein kinase C stimulates directional secretion of PGF(2alpha) from both surfaces of the epithelial cells.
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PMID:Directional secretion of prostaglandin F(2alpha) by polarized luminal epithelial cells from pig endometrium. 1075 47

Two experiments were conducted, aimed at improving the practicability of the method for transcervical embryo collection in Boer goats described by Pereira et al. [Pereira, R.J.T.A., Sohnrey, B., Holtz, W., 1998. J. Anim. Sci. 76, 360-363]. Invention of a hammock-like restraining device, use of a wider-bore flushing catheter and a modified flushing mode contributed toward this end. The importance of a luteolytic prostaglandin F(2alpha)-treatment [Pereira et al., 1998] was confirmed. In Experiment 1, administration of PGF(2alpha) 8h before does are flushed, increased the recovery rate from 43 to 79% (P<0.05). Advancing the PG F(2alpha)-treatment to 24h before flushing was instrumental in further enhancing embryo recovery rate. The amount of time required for flushing was reduced by about 20min (P<0.05) and the number of embryos recovered from the first 10 out of 30 flushes amounted to more than 80%, compared to 50% (P<0.05) when treating 8h before flushing. Administration of 1IU of oxytocin at the onset of flushing did not have any significant effect. When applying the findings of this investigation, the time required for flushing may be reduced from about 4h [Pereira et al., 1998] to less than 45min per doe and the required number of person involved decreased from four to two persons.
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PMID:Transcervical embryo collection in Boer goats. 1076 Apr 56

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