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

The effects of PGI-salt and PGI-2 methyl ester on intrauterine pressure (IUP) and uterine electromyographic activity (EMG) were examined in vivo in non-pregnant ovariectomized sheep. PGI-2 salt and PGI-2 methyl ester (50--200 micrograms) reduced significantly the frequency and amplitude of IUP cycles and also inhibited the associated uterine EMG activity. Injections of oxytocin (50 mU) or PGF-2 alpha (2 micrograms) partly overcame the inhibiton of IUP induced by the PGI-2 methyl ester. These results suggest that endogenous PGI-2 may be involved in the regulation of uterine activity in sheep.
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PMID:Inhibition by PGI-2 of myometrial activity in vivo in non-pregnant ovariectomized sheep. 675 Jan 8

Uterine horns for castrated, estrogen-treated rats wee superfused for 6 hours in 95% O2/5% CO2 at 37 degrees C. The method of superfusion in which medium flows separately over the inner and outer surfaces of the horn allows prostaglandin synthesis in the myometrium and endometrium to be measured independently while their anatomical relationship is undisturbed. Prostaglandins were measured by radioimmunoassay. They myometrium formed more 6-keto-PGF1 alpha than PGF whereas the opposite was true of the endometrium. Production rates of TxB2 in both tissues were relatively low. The addition of inophore A-23187, oxytocin or phenylephrine to the superfusion medium not only increased the myometrial production rates of both 6-keto-PGF1 alpha and PGF but also increased the ratio of 6-keto-PGF1 alpha:PGF. Neither ionophore nor phenylephrine affected the rate of prostaglandin synthesis in the endometrium whereas oxytocin caused a significant increase in the production rate of PGF. We conclude that the large amounts of 6-keto-PGF1 alpha in the myometrial superfusate probably originate in both the smooth-muscle cells of the myometrium and the endothelium of the myometrial blood vessels. The differential responses to ionophore A-23187, phenylephrine and oxytocin suggest differences in the mode of their regulation of prostaglandin synthesis.
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PMID:Differential production of PGF and 6-keto-PGF1 alpha by the rat endometrium and myometrium in response to oxytocin, catecholamines and calcium ionophore. 677 83

Spontaneous intrauterine pressure cycles were abolished for periods of several hours in ovariectomized non-pregnant ewes within 8 h of an injection of 50 micrograms oestradiol-17 beta. Following the quiescent period, a phase of intense uterine activity ensued for several hours before again being replaced by several hours of quiescence. This active/inactive cycle disappeared after 2-4 days if further daily injections of oestradiol were not given. During the quiescent periods the uterus retained its responsiveness to oxytocin and PGF-2 alpha. Increasing the dose of oestradiol failed to prolong the periods of quiescence.
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PMID:Oestradiol-17 beta both inhibits and stimulates myometrial activity in ewes in vivo. 683 31

Prostaglandins (PGs) are thought to have an important function in the initiation and/or propagation of parturition. To define the relationship of individual PGs to one another and compare their alterations with gestational age, PGF, PGE, 6-keto-PGF1 alpha (6KF) and thromboxane B2 (TxB2) were measured in uterine and placental tissue and uterine venous plasma of rats at Days 15, 18, 19, 20, and 21 of pregnancy and at delivery (Day 21 1/2). In addition, concomitant measurements of peripheral plasma estradiol (E2), estrone (E1) and progesterone (P) and pituitary oxytocin (OT) content, putative regulators and/or modulators of PG metabolism, were determined. Significant enhancements (P less than 0.05) in uterine 6KF, TxB2, PGF and PGE concentrations (ng/mg DNA) were detected by Day 20 compared to Day 15 of pregnancy and further dramatic increases were found on Day 21 and at delivery. Although uterine 6KF was present in the highest concentrations, PGF showed the greatest increment from Day 15 to delivery. No alterations in uterine venous plasma PGE or PGF concentration were found with gestational age but 6KF and TxB2 showed significant increases at delivery. The placental concentrations of PGs were approximately 1/50 of uterine tissue. Placental PGE and PGF concentrations (ng/mg DNA) increased only slightly at delivery but the augmentation in 6KF and TxB2 levels were of greater magnitude. Significant increases in E2 and E1 with reciprocal decreases in P occurred on Day 21 of pregnancy. In contrast, pituitary OT content showed no alterations at any of the days examined. These results are consonant with the hypothesis that uterine PGs have an important function in parturition and uterine-placental physiology, and suggest that an increasing estrogen/P ratio at the end of pregnancy is related to enhanced uterine PG levels.
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PMID:Alterations in reproductive tissue prostaglandins E and F, 6-keto-prostaglandin F1 alpha and thromboxane B2 with gestational age in the rat. 689 17

The concentration of specific oxytocin receptors increases during pregnancy and reaches a maximum at term after the onset of spontaneous labour. This constitutes a biochemical explanation for the well-known increase of oxytocin sensitivity during pregnancy. Oxytocin receptors were also found in human decidua and their concentration increased similarly. Based on these results the hypothesis was set up that oxytocin leads to an increase in prostaglandin production though specific receptors in decidua. Under specific incubation circumstances oxytocin indeed increased prostaglandin E and prostaglandin F synthesis of decidual tissue. In induction of labour with oxytocin PGF-levels in the maternal peripheral plasma increased significantly in all women in whom induction was successful. Since it is known that the fetus secretes considerable amounts of oxytocin in case of labour of spontaneous onset the hypothesis was set up that fetal oxytocin may initiate human labour by the mechanisms described above.
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PMID:[Does fetal oxytocin initiate human labour? A hypothesis]. 692 6

A group of 22 postpartum Holstein Friesian cows showing abnormal uterus were divided into two groups and treated with a) PGF(2)alpha or b) diethylstilboestrol and oxytocin. Most blood P(4) values were under 0.5 ng/mL whereas E(2) blood level was higher than in normal cycling cows. The report emphasizes the need for a careful clinical examination in order to apply the proper therapy.
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PMID:Metritis following parturition: serum progesterone and 17 beta-oestradiol levels. The significance of the corpus luteum and the advisability of using a luteolytic agent as a treatment. 718 34

In preliminary studies 5 of 6 heifers given oxytocin subcutaneously on Day 2--6 of the oestrous cycle had depressed progesterone levels by Day 5, and each had a precocious oestrus and a normal preovulatory LH surge. Oxytocin treatments given once daily on Days 5 and 6, or twice daily on Day 5 and 6 or 4, 5 and 6 resulted in shortened cycles and lower jugular progesterone concentrations in 1 of 5, 2 of 4 and 4 of 5 heifers, respectively. On the basis of these data, uterine venous and ovarian arterial catheters were inserted into 17 animals on Day 3 of the oestrous cycle and oxytocin treatments were given twice daily on Days 4, 5 and 6. Oxytocin treatment significantly depressed jugular progesterone levels by Day 8 and increased uterine venous prostaglandin (PG) F concentrations between 30 and 240 min after each injection. No changes of PGF concentrations occurred in uterine venous blood in control heifers, or in ovarian arterial blood from oxytocin-treated or control animals. It therefore appears that some factor other than PGF or a mechanism other than local veno-arterial transfer of PGF is involved in mediating the inhibitory effects of oxytocin on bovine corpus luteum function.
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PMID:Concurrent uterine venous and ovarian arterial prostaglandin F concentrations in heifers treated with oxytocin. 719

Myometrial activity was abolished abruptly but reversibly in 4 out of 5 ewes by the intravenous injection of 1 mg (500 GPU) porcine relaxin. Recovery began only after about 90 min and was not complete until 3-4 h after the injection. During the relaxin-induced inhibition the myometrium responded to oxytocin administered intravenously in doses of 250 mU. One ewe received intrauterine infusions of 2.5 and 5.0 microgram PGF-2 alpha per min during the period of relaxin inhibition: the former dose evoked a slight, and the latter a marked, response from the myometrium. The rate of rise of intrauterine pressure and the mean amplitude of pressures cycles were significantly depressed at 1, 1.5 and 2 h after the relaxin injection.
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PMID:Relaxin inhibits myometrial activity in the ovariectomized non-pregnant ewe. 720 86

In the present study we have investigated the effect of oxytocin on the production of prostaglandins E and F (PGE and PGF) by human decidua, amnion, and myometrium in vitro. We found that oxytocin causes a significant increase in the production of both PGE and PGF in the decidua and in the production of PGE in the amnion. In the myometrium the stimulatory effect of oxytocin on PGF production was small and not statistically significant, and PGE production was not affected at all. On the basis of these results, we propose that oxytocin provides the stimulus for the accelerated prostaglandin production in decidua and fetal membranes at the onset of labor. Since oxytocin levels rise in the fetal circulation at this time, the oxytocin stimulus may be of fetal origin as well as of maternal origin.
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PMID:Oxytocin and the initiation of human parturition. II. Stimulation of prostaglandin production in human decidua by oxytocin. 731 96

Oxytocin stimulates secretion of endometrial prostaglandin (PG) F2 alpha and induces endometrial phosphoinositide hydrolysis around the time of regression of the corpus luteum (CL) in cows. This study investigated the relationship between endometrial oxytocin receptors, oxytocin-stimulated phosphoinositide hydrolysis and PGF 2 alpha secretion in vitro, and plasma concentrations of ovarian steroids before and during CL regression in cyclic heifers (i.e., Days 13-19 post-estrus). Reproductive tracts were collected from 16 cyclic heifers on Days 13 (n = 5), 16 (n = 5), and 19 (n = 6). Decreases in mean CL weight (4.7, 4.6, and 3.0 +/- 0.6 g for Days 13, 16, and 19, respectively; p < 0.05) and plasma progesterone (12.2, 10.5, and 4.3 +/- 1.5 ng/ml for Days 13, 16, and 19, respectively; p < 0.01) were detected between Days 16 and 19, indicating that CL regression had been initiated in the group of Day 19 heifers. Mean concentration of plasma estradiol (3.4, 3.8, and 5.6 +/- 1.7 pg/ml for Days 13, 16, and 19, respectively) did not differ significantly (p > 0.5) among days of the estrous cycle. Concentration of endometrial oxytocin receptors increased (p < 0.06) during the estrous cycle (36, 49, and 789 +/- 234 fmol/mg protein on Days 13, 16, and 19, respectively), but the greatest increase (p < 0.05) occurred between Days 16 and 19. Similarly, incorporation of [3H]inositol into endometrial inositol phosphates induced in vitro with 100 nM oxytocin also increased (p < 0.01) during the estrous cycle (5121 vs. 5819, 4529 vs. 7239, and 5888 vs 68,096 +/- 18,564 dpm/g tissue for control vs. oxytocin-treated endometrium on Days 13, 16, and 19, respectively) with the greatest increase (p < 0.01) in responsiveness to oxytocin occurring between Days 16 and 19.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Relationships among endometrial oxytocin receptors, oxytocin-stimulated phosphoinositide hydrolysis and prostaglandin F2 alpha secretion in vitro, and plasma concentrations of ovarian steroids before and during corpus luteum regression in cyclic heifers. 838 49


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