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)

(1) Oxytocin is synthesized in the luteal cells of all species so far studied, including the human. Vasopressin is also synthesized, but at a much lower rate. (2) The oxytocin-neurophysin gene is expressed in granulosa cells and granulosa-derived luteal cells but not in theca cells. Ovulation or spontaneous luteinization initiates the gene expression which peaks in the early luteal phase and ceases around mid-cycle. (3) Luteal oxytocin concentrations rise with considerable delay after the peak of specific mRNA and reach maximal levels around mid-cycle. Oxytocin concentrations fall to low levels in the late luteal phase and in pregnancy. (4) Thecal tissue produces substances such as catecholamines and ascorbic acid that stimulate oxytocin secretion in granulosa cells. The adrenergic innervation of thecal tissue provides a source of catecholamines and may therefore serve a modulatory function in ovarian oxytocin secretion. (5) Oxytocin has little or no direct effect on luteal progesterone production. (6) Oxytocin inhibits LH-stimulated prostacyclin production in luteal cells of cows. Oxytocin may induce the release of PGF-2 alpha or lipo-oxygenase products from the ovary but this has not yet been documented. (7) PGF-2 alpha releases oxytocin from the ovary but does not turn off its synthesis. (8) The concept that ovarian oxytocin participates in the luteolytic process is gaining acceptance. In some species (sheep, goat) ovarian oxytocin acts as a hormone causing PGF-2 alpha release from the uterus. In others it acts in a paracrine or autocrine fashion on ovarian prostanoid production (cow, possibly primates).(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Oxytocin and ovarian function. 305 1

Corpora lutea from sheep and cows as well as human and primates contain both large and small steroidogenic cells exhibiting distinct functional properties. Only the small cells seem to be able to respond in vitro to LH stimulation by raising their progesterone secretion. However, the entire progesterone secretion of the corpus luteum has been shown to be regulated in vivo by LH in the primate. The LH steroidogenic action involves the activation of membrane adenylate cyclase whose molecular mechanism has been elucidated. Then a rise in intracellular cyclic AMP induces phosphorylation by a cyclic AMP dependent protein kinase of steroidogenic protein targets which have not yet been completely identified. In sheep and cows, luteolysis is believed to be the consequence of a series of reciprocal interactions between the corpus luteum whose large cells secrete pulses of oxytocin in response to PGF2 alpha luteolysin and the endometrium which secretes pulses of PGF2 alpha in response to oxytocin. The secretion of endometrial PGF2 alpha can only begin after the induction of endometrial receptors by estradiol, from the preovulatory follicles. Similarly in women and primates luteolysis, which does not require the presence of the uterus, could be the consequence of local reciprocal paracrine interactions between luteal cells of different types. These interactions are likely to involve PGF2 alpha' oxytocin and estradiol. The biochemical mechanism responsible for the inhibition by PGF alpha of LH induced progesterone secretion in luteal cells could involve a stimulation in the cell membrane of protein kinase C and the rise of cytosolic Ca+.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:[Recent concepts concerning the corpus luteum]. 307 52

We have investigated the effects of exogenous oxytocin and prostaglandin F2 alpha (PGF2 alpha) on the concentrations of prostaglandins E and F (PGE and PGF) in the utero-placental tissues in late pregnant rabbit. The subjects were 5 rabbits each on days 26, 27 and 30 of pregnancy. After one side of the uterine horn was excised as the control, 3,000 micrograms of PGF2 alpha, 10 microU of oxytocin or 1 ml of saline was administered to 2,2 and 1 rabbits as an iv bolus dose. After 10 minutes, the remaining side of the uterine horn was excised. The myometrium, fetal and maternal cotyledon, decidua and amnion were separated. The concentrations of PGE and PGE in each tissue were measured by radioimmunoassay after extraction. The highest concentration of PGE was observed in the fetal cotyledon and that of PGF in the decidua. The amniotic PGE concentration significantly decreased after the administration of both oxytocin and PGF2 alpha. The myometrial PGF concentration increased significantly after the administration of PGF2 alpha, and the degree of the increase in PGF became greater as pregnancy advanced. However, the myometrial PGF concentration did not increase after the administration of oxytocin.
 ...
PMID:Changes in the concentrations of prostaglandins E and F in the utero-placental tissues of late pregnant rabbit after the administration of oxytocin or prostaglandin F2 alpha. 316 8

Seven bilaterally ovariectomized heifers were used in 4 experiments and received: (1) saline injections, as control; (2) one injection of oestradiol (3 mg; i.v.); (3) two i.v. injections of oxytocin (100 i.u.) 6 h apart; or (4) one oestradiol injection 30 min after the first oxytocin injection and a second oxytocin injection 6 h later. All experiments were performed without progesterone and then after 7, 14 and 21 days of progesterone treatment. Frequent blood samples were taken for 1 h before and 7 h after the first injection of oxytocin or oestradiol for the measurement of 13,14-dihydro-15-keto-PGF-2 alpha (PGFM) by radioimmunoassay. After 7, 14 and 21 days of progesterone priming, oestradiol caused a significant increase (P less than 0.001) in plasma PGFM after 6 h but not before. After 7, 14 and 21 days of progesterone, there was a significant increase (P less than 0.005) in PGFM after the first oxytocin injection and a similar increase following the second. The oxytocin-induced increase in PGFM after 14 and 21 days of progesterone was significantly higher (P less than 0.001) 6 h after oestradiol injection than before the oestradiol injection. There was no significant effect of oestradiol on the response to oxytocin in animals that received no progesterone or in those animals that received progesterone for only 7 days. These results show that, under the influence of progesterone, oestradiol enhances the oxytocin-induced release of PGF-2 alpha, and suggest a possible synergistic action of these hormones for the induction of luteolysis in heifers.
 ...
PMID:Effects of progesterone and oestradiol-17 beta on oxytocin-induced release of prostaglandin F-2 alpha in heifers. 316

Bilateral perifusion devices were utilized for measurement of prostaglandin secretion by luminal and myometrial surfaces of porcine endometrium. Tissues were collected from Days 10, 12 and 14 pregnant, Day 14 cyclic and Day 14 estrogen-induced pseudopregnant gilts. Each tissue was placed into duplicate perifusion devices and perifused with Krebs-Ringer Bicarbonate solution at 3 ml/10 min for 2 h, fractions collected every 10 min and oxytocin (1 IU/ml) perifused during fractions 6-10 to the luminal side of one chamber and to the myometrial side of the other chamber. Secretion rates of PGF were higher (P less than 0.05) than PGE2 for each status. Secretion rates of PGF and PGE2 were higher (P less than 0.01) from the luminal side for Day 12 pregnant, Day 14 pregnant and Day 14 pseudo-pregnant gilts, whereas secretion was higher from the myometrial side for Day 10 pregnant and Day 14 cyclic gilts. Oxytocin increased (P less than 0.01) prostaglandin secretion from the luminal side regardless of reproductive status. Pregnancy at Day 12 and Day 14, as well as estrogen treatment, were associated with prostaglandin secretion in a luminal (exocrine) orientation versus a myometrial (endocrine) orientation for Day 14 cyclic and Day 10 pregnant gilts. These data indicate an estrogen associated switch between Days 10 and 12 of pregnancy from an endocrine to an exocrine secretion of prostaglandins.
 ...
PMID:Prostaglandin secretion by perifused porcine endometrium: further evidence for an endocrine versus exocrine secretion of prostaglandins. 316 10

Bilateral perifusion devices were utilized to measure prostaglandin secretion towards luminal and myometrial sides of bovine endometria. Tissues were collected at Day 17 post-estrus from cyclic (n = 4), pregnant (n = 5) and bred but subsequently non-pregnant (n = 6) cows. Tissue from each cow was placed into two perifusion devices, perifused with Krebs-Ringer Bicarbonate solution (3 ml/10 min) for 2.5 h and fractions collected every 10 min. Oxytocin (1 IU/ml) was perifused during fractions 7-12 to the luminal side of one device and to the myometrial side of the other device. Regardless of status, prostaglandin secretion rates (PGF and PGE2) were higher (P less than 0.01) from the luminal side than the myometrial side. Secretion rates of PGF were lower (P less than 0.01) for endometria from pregnant cows than for endometria from cyclic or bred/non-pregnant cows, whereas secretion rates of PGE2 were not affected by pregnancy status. Regardless of the side of perifusion, secretion rates of PGF and PGE2 from endometria of cyclic and bred/non-pregnant cows were elevated (P less than 0.01) throughout the period of oxytocin treatment, whereas prostaglandin secretion by endometria from pregnant cows was not stimulated by oxytocin. Decreased secretion of PGF from endometria of pregnant cows suggests that the corpus luteum and pregnancy are maintained because of an inhibition of endometrial prostaglandin synthesis or an inability to respond to stimulators of prostaglandin synthesis (i.e. oxytocin).
 ...
PMID:Prostaglandin secretion by perifused bovine endometrium: secretion towards the myometrial and luminal sides at day 17 post-estrus as altered by pregnancy. 316 11

Concentrations of progesterone, oxytocin and PGFM (pulmonary metabolite of PGF-2 alpha) were measured in plasma from peripheral blood samples collected from 5 fallow does every hour or 2 h for 12-h periods on Days 15-20 inclusive of the oestrous cycle (i.e. luteolysis). For 3 does that exhibited oestrus on Day 21, plasma progesterone concentrations fluctuated between 3 and 10 ng/ml on Days 15-18 inclusive. Thereafter, values declined progressively to attain minimum concentrations of less than 0.05 ng/ml on Day 20. Basal concentrations of plasma oxytocin and PGFM fluctuated between 5 and 20 pg/ml and 10 and 100 pg/ml respectively. Episodic pulses of plasma oxytocin (greater than 300 pg/ml) occurred on Days 15 and 16, whereas pulses of plasma PGFM (greater than 400 pg/ml) occurred on Days 19 and 20. There was little apparent correlation between episodic pulses of the two hormones. For 2 does that exhibited oestrus on Day 22, plasma progesterone concentrations declined to minimum values of 1.0-1.5 ng/ml by Day 20. One of these does showed very high levels of oxytocin secretion throughout the sampling period while the other showed an apparent paucity of oxytocin secretory periods. Two does hysterectomized on Day 13 of their second oestrous cycle failed to exhibit further oestrous cycles. Continual elevation of plasma progesterone concentrations (2-6 ng/ml) for an 8-month period indicated persistence of the corpus luteum after hysterectomy. It is concluded that luteolysis in fallow deer involves episodic secretion of both oxytocin and PGF-2 alpha.
 ...
PMID:Hormonal changes during luteal regression in farmed fallow deer, Dama dama. 318 58

Conceptus secretory proteins (oCSP) were obtained from medium in which sheep conceptuses, collected on Day 16 of pregnancy, were cultured for 30 h. A portion of the culture medium (500 ml) was prepared for intrauterine infusion by concentrating the proteins by Amicon ultrafiltration (Mr 500 cutoff). A second portion (500 ml medium) was used to purify sheep trophoblast protein one (oTP-1). Proteins remaining after oTP-1 purification were concentrated and then passed through an anti-oTP-1 sepharose CL-4B affinity column to remove any remaining oTP-1 (oCSP-oTP-1). Serum proteins (oSP) were collected from a Day-16 pregnant ewe and diluted for infusion. Catheters were placed in the uterus of cyclic (Day 10) ewes. The following combinations of proteins were infused: 0.75 mg oCSP + 0.75 mg oSP (5 ewes), 0.75 mg oCSP - oTP-1 + 0.75 mg oSP (4 ewes), 0.05 mg oTP-1 + 1.45 mg oSP (5 ewes) and 1.5 mg oSP only (5 ewes). Infusions were twice daily on Days 12 and 13 (08:00 and 17:00 h) and once on Day 14 (08:00 h). On Day 14, ewes were injected intravenously at 08:00 h with 0.5 mg oestradiol-17 beta. Blood sampling began 30 min before oestradiol injection and continued every 30 min for 10 h. On Day 15 ewes received 10 i.u. oxytocin intravenously (08:00 h). Blood samples were collected 10 min before oxytocin and every 10 min for 1 h after oxytocin injection. Concentrations of prostaglandin (PG) F, PGE-2/PGE-1 (PGE) and 13,14-dihydro-15-keto-PGF-2 alpha (PGFM) were measured by specific radioimmunoassay. Ewes treated with oTP-1 and oCSP had longer (P less than 0.05) interoestrous intervals (27 and 25 days, respectively) compared to ewes treated with oSP and oCSP--oTP-1 (19 and 19 days, respectively) (s.e.m. = 1.56 days). These results indicate that oTP-1 alone is as potent as total conceptus secretory proteins in extending luteal maintenance. Ewes treated with oTP-1 and oCSP had no increase in PGF after oestradiol injection while production of PGF did increase 6-10 h after oestradiol in ewes treated with oSP and oCSP--oTP-1. PGFM was correlated with PGF concentrations (r = 0.57, P less than 0.01) although presence or absence of increases in production of PGFM for the treatment groups were not the same as those for PGF. No effects of treatment on PGE were detected.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:Effect of ovine conceptus secretory proteins and purified ovine trophoblast protein-1 on interoestrous interval and plasma concentrations of prostaglandins F-2 alpha and E and of 13,14-dihydro-15-keto prostaglandin F-2 alpha in cyclic ewes. 319 68

Two experiments were conducted to determine if the ability of oxytocin to stimulate release of prostaglandin (PG)F2 alpha from ovine uterine tissue involved activation of phospholipase C (PLC). In the first experiment, 9 ewes were injected with progesterone for 11 d (12 mg/d, im). On days 11 and 12, ewes received an injection of estradiol (100 micrograms, im). Caruncular endometrial tissue was collected on d 13 and incubated in the presence or absence of oxytocin (10(-6) M). Concentrations of PGF2 alpha and its metabolite, 13,14-dihydro-15-keto-PGF2 alpha (PGFM), in culture media were determined by radioimmunoassay. PLC activity was determined by measuring the intracellular accumulation of 3H-inositol phosphates after preincubation with 3H-inositol. Concentrations of PGF2 alpha and total PGF (PGF2 alpha + PGFM) in culture media were greater for explants treated with oxytocin than for controls (p. less than .02, p less than .06, respectively). A similar effect of oxytocin on intracellular concentrations of 3H-inositol phosphates was observed (p less than .01). A second experiment was conducted to determine if agonists of second messengers, produced by activation of PLC, could stimulate release of PGF2 alpha from ovine endometrial tissue. Seven ewes were treated with progesterone and estradiol as in experiment 1. Explants of caruncular tissue from each ewe were incubated with 1) control medium, 2) A23187 (10(-5) M), 3) oxytocin (10(-6) M), 4) phorbol 12-myristate 13-acetate (PMA, 10(-7) M), 5) PMA + A23187 and 6) PMA + oxytocin. Significant stimulatory effects of oxytocin, PMA and A23187 on concentrations of PGF2 alpha and total PGF in culture media were observed (p. less than .05, p less than .1, p less than .1, respectively). In conclusion, oxytocin stimulated release of PGF2 alpha and activity of PLC in explants of ovine endometrial tissue in vitro. Second messengers associated with activation of PLC enhanced release of PGF2 alpha from ovine endometrial tissue.
 ...
PMID:Role of phospholipase C in mediating oxytocin-induced release of prostaglandin F2 alpha from ovine endometrial tissue. 324 71

The variety of peptides synthesized by the corpus luteum (relaxin, vasopressin, oxytocin and oxytocin-related neurophysin) and their possible intracellular effects are reviewed. After luteinization of the granulosa cells and in response to LH and FSH, the output of oxytocin is increased. In addition, insulin-like growth factor is a very potent stimulus of oxytocin secretion. Although luteal cells respond to gonadotrophins by increased production of progesterone, there is no further secretion of oxytocin. Oxytocin is localized in large luteal cells which seem not to be under the direct control of gonadotrophins. Synthesis of luteal oxytocin seems to occur during the early luteal phase according to measurements of oxytocin mRNA. Highest tissue concentrations and secretion under in-vitro conditions were observed during the mid-luteal phase, and so synthesis, storage and secretion are unlikely to occur concomitantly. Under in-vitro conditions, oxytocin is secreted concomitantly with neurophysin and progesterone, and there appears to be some form of communication between small and large luteal cells for the secretion of progesterone and oxytocin under in-vivo conditions. Evidence has been obtained that oxytocin may have local effects in the ovary by inhibition of secretion (synthesis ?) of progesterone, especially during the early luteal phase. A mechanism can be suggested whereby, under physiological conditions, oxytocin may delay the increase of progesterone by inhibition of progesterone secretion and therefore delay down regulation of its own receptor. This would prolong the life-span of the CL and the oestrous cycle. Exogenous progesterone given on Days 1-4 shortens the cycle to about 12 days. The best evidence that oxytocin may be involved in controlling luteolysis comes from immunization experiments in ewes and goats, but there is no clear evidence of this type for cattle. Basal concentrations of oxytocin at the end of the luteal phase may interact with oxytocin receptors after the inhibitory effect of progesterone in the uterus is reduced, thus initiating synthesis of PGF-2 alpha.
 ...
PMID:Luteal peptides and intercellular communication. 330 25


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