Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Blood samples were collected frequently from permanent catheters placed in the aorta and caudal vena cava of 36 heifers in order to monitor the release pattern of LH, FSH, progesterone, oestradiol-17 beta, oxytocin, PGF-2 alpha, PGE-2 and PGI-2 (determined as its 6-keto-PGF-1 alpha metabolite). The frequency of secretory bursts of both gonadotrophins and progesterone was similar in early pregnant and cyclic animals, whereas the amplitude of LH and progesterone increased between 2 and 4 weeks of gestation. Concentrations of circulating oestradiol-17 beta and oxytocin were already lower at Days 4-7 in pregnant than in cyclic animals. Oestradiol-17 beta originated after Day 14 from the uterus rather than the ovary. A sustained release of oxytocin most probably from the posterior pituitary gland and a concomitant decrease of progesterone occurred in about two-thirds of pregnant animals during Days 19-23. Insemination could induce releases of PGF-2 alpha lasting up to 2 h. In addition, basal concentrations of PGF-2 alpha during the first 6 days after oestrus were approximately 2-fold higher in inseminated than in non-inseminated cyclic heifers. A parallel increase of PGF-2 alpha and PGI-2 occurred between Days 30 and 33 of gestation. Early embryonic mortality resulted, at least up to Day 35, in 4-7 concomitant secretory bursts of PGF-2 alpha and luteal oxytocin. There was a delay of 20-26 h between the first and second release. The present results from in-vivo experiments point towards major endocrine changes in cattle within a few days after conception, resulting in an early inhibition of follicular oestradiol-17 beta and luteal oxytocin facilitating the suppression of luteolytic releases of PGF-2 alpha.
 ...
PMID:Sequences of pituitary, ovarian and uterine hormone secretion during the first 5 weeks of pregnancy in dairy cattle. 250 92

Oestrous cycles of goats were synchronized hormonally. Immunoreactive oxytocin was undetectable (less than 0.1 ng/mg protein) in media from granulosa cells isolated before the LH surge for small (1-2 mm), medium (3-5 mm) and large (greater than 5 mm diameter) follicles when cultured for 24 h without or with added hormones. Granulosa cells from large and medium, but not small, follicles isolated 6-12 h after spontaneous preovulatory LH surges secreted high concentrations of oxytocin (4-12 ng/mg protein). Addition of PGE-2 (1 microgram/ml) caused a further significant (P less than 0.05) increase in oxytocin secretion by cultured granulosa cells, whereas PGF-2 alpha, FSH and LH were ineffective when added to culture media. Ovarian venous blood and granulosa cells were collected at 0, 6, 12 or 18 h after GnRH injection in hormonally synchronized goats. Peripheral serum LH values were increased significantly in all but 2 of 22 goats within 2 h of GnRH injection. At the earliest sampling time after GnRH (6 h), ovarian venous levels of oxytocin were increased significantly from basal levels of 0.4 pg/ml to 2.4 pg/ml. Oxytocin concentrations in follicular fluid increased from a basal value of 67 pg/ml to 155 pg/ml by 6 h and to 372 pg/ml by 18 h after GnRH injection. Oxytocin secretion by cultured granulosa cells was not increased significantly by 6 h (0.1 ng/mg protein) but rose to 1.4 and 3.5 ng/mg protein at 12 and 18 h, respectively. Approximately parallel increases occurred in progesterone in ovarian venous blood and granulosa cell culture media over the same time period. (ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Preovulatory biosynthesis and granulosa cell secretion of immunoreactive oxytocin by goat ovaries. 251 89

Jugular administration of 200 micrograms PGI-2 salt significantly reduced spontaneous uterine activity in ovariectomized, oestrogen-primed goats; the effect was acute and persisted for about 3 h. Peripheral plasma concentrations of 6-keto-PGF-1 alpha, the stable metabolite of PGI-2, decreased to 50% of initial values after 30 min; but at the start of uterine recovery were in excess of 2 ng.ml-1. Uterine reactivity to both oxytocin and PGF-2 alpha after PGI-2 administration was unaffected.
 ...
PMID:Effect of PGI-2 on uterine activity in vivo in non-pregnant ovariectomized goats (Capra hircus). 251 31

Sheep conceptuses secrete a protein, ovine trophoblast protein-1 (oTP-1), between days 10 and 21 of gestation, that is responsible for establishment of pregnancy. oTP-1 inhibits uterine production of episodic release of prostaglandin (PG) F2 alpha (PGF) necessary for luteolysis and produced in response to oestradiol and oxytocin. oTP-1 does not compete with oxytocin for binding to its receptors or interfere with oxytocin stimulation of the inositol phospholipid second messenger system after oxytocin receptors are formed. However, oTP-1 may affect synthesis of oxytocin, oestrogen and/or progesterone receptors to alter the ability of the uterus to produce episodic pulses of PGF in response to episodic pulses of oxytocin. Porcine conceptuses secrete oestrogens between days 10 and 15 of pregnancy that are essential for establishment of pregnancy. Oestrogens, directly or indirectly, alter secretion of PGF from an endocrine direction (toward the uterine vasculature) to an exocrine direction (toward the uterine lumen). PGF sequestered in the uterine lumen is unavailable to exert a luteolytic effect on the corpus luteum (CL). Pig conceptus secretory proteins stimulate uterine production of PGF and PGE, but do not appear to be responsible for inhibition of luteolysis. Conceptus secretory proteins of sheep and pigs include proteins that have antiviral activity and are considered interferons. In sheep, oTP-1 has antiluteolytic, immunosuppressive, antiviral and possibly antiproliferative properties. The specific pig conceptus secretory protein(s) possessing antiviral activity has not been established. Unlike oTP-1, however, pig interferon-like protein(s) does not appear to possess antiluteolytic activity.
 ...
PMID:Establishment of pregnancy in sheep and pigs. 268 7

Bovine conceptuses exert an antiluteolytic (anti-PGF-2 alpha) effect on the uterus by decreasing the secretion of PGF that results in maintenance of the CL. Basal and oxytocin-stimulated secretion rates of PGF from perifused endometrium are lower at Day 17 of pregnancy than at Day 17 of the oestrous cycle, probably because of increased amounts of an intracellular, endometrial PG-synthesis inhibitor which is present in the 100,000 g cytosolic supernatant, is proteinaceous, and acts in a noncompetitive manner with respect to arachidonic acid. The antiluteolytic signal in bovine conceptus secretory proteins (bCSP) is bovine trophoblast protein-1 (bTP-1), a group of 7 isomers of N-linked glycoproteins in two size classes (22,000 high-mannose and 24,000 complex types) that are related immunologically to ovine trophoblast protein-1 (oTP-1). Incubation of endometrial explants of Day-17 cyclic cows with bCSP and bTP-1 induced PG-synthesis inhibitor activity and reduced PGF secretion. Intrauterine infusion of bTP-1 from Days 15.5 to 21 extended the interoestrous interval from 19.5 to 26.0 days. Intrauterine infusion of interferon-alpha I 1 through the cervix from Day 15.5 to 21 extended the interoestrous interval from 22.8 to 26.8 days. Platelet-activating factor (PAF) and interferon-alpha I 1 alter PG secretion of endometrial explants (PAF decreases PGF and increases PGE-2; interferon-alpha I 1 does not alter PGF and increases PGE-2 secretion) but neither induces activity of the endometrial PG-synthesis inhibitor. In conclusion, bovine conceptuses exert a paracrine effect through the secretion of bTP-1 to induce an endometrial intracellular inhibitor of PGF synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Antiluteolytic effects of bovine trophoblast protein-1. 281 Feb 37

Two mares received PGF-2 alpha twice daily until abortion and 2 mares received a combined treatment with oestradiol benzoate and oxytocin. The mares were about 150 days pregnant. The PG-treated animals aborted after 37 and 61 h, respectively, and the fetuses were expelled in intact fetal membranes. The other 2 mares aborted 13 and 27 h after the first oxytocin injection, respectively, and showed strong uterine contractions and expelled the fetuses in disrupted fetal membranes. Concentrations of 15-ketodihydro-PGF-2 alpha increased both after PG and oxytocin injections and in association with the abortion, but after the PG-induced abortion there was an immediate return to basal levels and after the oxytocin-induced abortion there was a large increase in the concentrations, indicating damage of the uterus. Progesterone and relaxin concentrations followed the placental function and decreased in association with the abortions. Oestrone sulphate values differed in the two groups; the oxytocin-treated animals showed a rapid decrease while the mares treated with PG showed first a marked increase and then a decrease. Concentrations of PMSG appeared to be unaffected by the abortions.
 ...
PMID:Hormonal changes associated with induced late abortions in the mare. 282 69

Continuous intravenous infusion of oxytocin (3 micrograms/h) between Days 13 and 21 after oestrus delayed return to oestrus by 7 days (length of cycle 23.3 +/- 0.6 days compared to 16.6 +/- 0.2 days in control ewes). At a lower infusion rate (0.3 micrograms/h) oxytocin delayed luteolysis in only 2 of 5 ewes. Treatment from Day 14, when luteolysis had already begun, was ineffective. Delay of luteal regression by oxytocin had no effect on the length of subsequent cycles. Measurement of circulating progesterone concentrations and luteal weight showed that prolongation of the oestrous cycle was due to prevention of luteal regression. Luteal regression and behavioural oestrus were induced during continuous oxytocin administration begun on Day 13 when cloprostenol was given on Day 15 (mean cycle length, 17.3 +/- 0.21 days). Continuous oxytocin infusion from Day 13 blocked the rise in uterine oxytocin receptor concentrations which normally precedes oestrus. Mean receptor concentrations in caruncular and intercaruncular endometrium and in myometrium were 76, 36 and 9 fmol/mg protein on Day 17 in ewes receiving continuous oxytocin (3 micrograms/h); in control ewes these values were 675, 638 and 130 fmol/mg protein respectively at oestrus. Receptor concentrations on the day of oestrus in ewes receiving oxytocin and cloprostenol were not significantly different from those in control ewes (649, 852, and 109 fmol/mg protein respectively). Since cloprostenol, a PGF-2 alpha analogue, overcame the antiluteolytic action of oxytocin, it is suggested that continuous oxytocin treatment may inhibit uterine production of PGF-2 alpha, possibly by down regulating the uterine oxytocin receptor.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Continuous infusion of oxytocin prevents induction of uterine oxytocin receptor and blocks luteal regression in cyclic ewes. 299 86

The secretion of oxytocin by the corpus luteum is thought to stimulate the episodic release of PGF-2 alpha from the uterus, thereby contributing to luteolysis. In pregnancy corpus luteum function is maintained, and secretion of oxytocin, or its actions on the uterus, appear to be inconsistent with the successful establishment of gestation. Protection against the effects of oxytocin is ensured by a number of mechanisms, including the cessation of luteal oxytocin secretion, which is evident by Day 20 after mating in sheep, and the maintenance of low levels of the oxytocin receptor in the uterus.
 ...
PMID:Ovarian oxytocin and the maternal recognition of pregnancy. 300 1

Steroid-primed, ovariectomized ewes were treated intravenously with 2 doses of 1 microgram oxytocin at intervals of 1, 2, 4 or 6 h. The initial dose resulted in increases in 13,14-dihydro-15-keto-PGF-2 alpha in the peripheral circulation from 173 to 667 pg/ml within 5 min; subsequent doses caused responses of 23 +/- 1, 23 +/- 6, 54 +/- 12 and 62 +/- 10% respectively of the initial dose. Concentrations of oxytocin receptor in myometrium, caruncular endometrium and intercaruncular endometrium were, respectively, 185 +/- 33, 128 +/- 7 and 105 +/- 14 fmol/mg protein at 2 h after saline injection and 147 +/- 27, 195 +/- 52 and 170 +/- 50 fmol/mg protein at 2 h after administration of 1 microgram oxytocin. The dose of oxytocin administered was shown to raise circulating concentrations to levels characteristic of those observed during spontaneous episodes of release of oxytocin at luteolysis. Oxytocin administration therefore results in transitory uterine refractoriness which may be due to failure of a post-receptor response and this may contribute to the episodic nature of uterine prostaglandin secretion.
 ...
PMID:Transient uterine refractoriness after oxytocin administration in ewes. 301 57

Administration of oestradiol-17 beta benzoate on Days 9 and 10 of the oestrous cycle resulted in episodic secretion of PGF-2 alpha (as indicated by elevated circulating concentrations of 13,14-dihydro-15-ketoprostaglandin F-2 alpha) and a decline in circulating progesterone. Release of PGF-2 alpha began 35 +/- 3 h after first injection of oestrogen and progesterone concentrations declined from 42 +/- 3 h. Secretion of oxytocin, which was first observed 26 +/- 3 h after oestrogen treatment, preceded secretion of PGF-2 alpha; 69% of pulses of oxytocin coincided with episodes of PGF-2 alpha secretion. Uterine oxytocin receptor concentrations were raised in ewes treated with oestrogen, increases occurring in caruncular endometrium and myometrium by 12 h after treatment and in intercaruncular endometrium by 24 h. Raised receptor concentrations were followed at 24 h by increases in the incorporation of [3H]inositol into phosphatidylinositol and in the hydrolysis of labelled tissue phosphoinositides in response to oxytocin in slices of caruncular endometrium incubated in vitro. The following sequence of events is therefore suggested to occur at oestrogen-induced luteolysis: induction of the oxytocin receptor; increased turnover of phosphoinositides; onset of episodic secretion of PGF-2 alpha; and functional luteolysis.
 ...
PMID:Effects of a luteolytic dose of oestradiol benzoate on uterine oxytocin receptor concentrations, phosphoinositide turnover and prostaglandin F-2 alpha secretion in sheep. 303 33


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>