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

The subcellular distribution of progesterone and oxytocin within the ovine corpus luteum was investigated using differential and density gradient centrifugation. Progesterone and oxytocin were associated with particles which sedimented to a density of 1.049-1.054 g/ml and 1.054-1.061 g/ml respectively. Particle-associated progesterone did not, however, display physical or biochemical characteristics consistent with its storage within secretory granules. When particle-associated progesterone was incubated in HEPES buffer at 37 degrees C, 70% of the total progesterone was recovered in the incubation medium. The remaining stable particle-associated progesterone was not affected by treatments which stimulated oxytocin release and which have been shown to cause the release of peptides and biogenic amines from secretory granules. These results suggest that particle-associated progesterone represents the intercalation of progesterone into cell membranes and they do not support the hypothesis that progesterone is stored, in a protein-bound form, in luteal secretory granules.
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PMID:Comparison of particle-associated progesterone and oxytocin in the ovine corpus luteum. 394 30

The uterine electromyogram (EMG) and intrauterine pressure curves (IUP) were investigated as indicators of myometrial activity in chronically instrumented, ovariectomized ewes. Spontaneous electrical activity was characterized by rhythmic patterns of trains of bursts accompanied by IUP waves. Administration of adrenergic (propranolol or phentolamine) or cholinergic (atropine) blocking agents had no effect on spontaneous uterine activity. Both oxytocin and PGF2 alpha appeared to stimulate spontaneous myometrial activity. 17beta-Estradiol temporarily depressed uterine activity in a dose-dependent fashion. The period of relaxation was followed by a pronounced increase in activity. Progesterone treatment resulted in long-term suppression of myometrial activity. Oxytocin and PGF2alpha increased EMG and IUP activity during estradiol suppression but not after progesterone treatment. These results indicate that the myometrium is active in chronically instrumented, ovariectomized ewes. The autonomic nervous system or its receptors do not play a role in the maintenance of spontaneous myometrial activity, estradiol and progesterone suppress myometrical activity but by different mechanisms.
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PMID:Modulation of spontaneous myometrial activity in chronically instrumented ovariectomized sheep. 398 50

We have previously reported that intracerebroventricular (ICV) administration of oxytocin (OXY) produces a significant increase in maternal behavior in ovariectomized (OVXed) rats given a single priming dose of estrogen. Arginine vasopressin (AVP) has a weaker and more delayed but significant facilitating effect on the onset of maternal behavior. Other investigators have demonstrated that prolonged treatment of OVXed nulliparous rats with estrogen and progesterone followed by withdrawal of progesterone shortens the latency of onset of maternal behavior. We hypothesized that ovarian steroids increase the onset of maternal behavior by a central mechanism involving OXY and possibly AVP. To test this nulliparous Sprague Dawley rats were given SC one Silastic capsule containing 4.4 mg of 17 beta-estradiol eight days after OVX and three capsules each containing 40 mg of progesterone ten days after OVX. Progesterone capsules were removed on the 20th day after OVX, 24 hrs before the introduction of three rat pups (1-5 days old). One hr prior to introduction of pups animals received ICV 10 microliters of anti-oxytocin antiserum (AOA), anti-arginine vasopressin antiserum (AVA), anti-neurotensin antiserum (ANA), normal rabbit serum (NRS), AOA + 250 ng OXY or no ICV infusion. Animals receiving AOA displayed significantly less maternal behavior compared to animals receiving NRS, ANA or no ICV infusion over the first two, six and 25 hrs of pup contact. OXY significantly reversed the inhibitory effect of AOA in the first two hrs of pup contact. AVA significantly decreased the onset of maternal behavior compared to ANA or no ICV infusion over the first six hrs of pup contact.
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PMID:Oxytocin antiserum delays onset of ovarian steroid-induced maternal behavior. 400 Apr 28

Oestrous rats were anaesthetized with pentobarbital, one of the femoral arteries and veins and one of the ovarian veins were cannulated, and a thin polyethylene cannula was fixed in the ovarian bursa. Five-min blood fractions were collected from the ovary for 50 min. Following the control fractions 15 mU of oxytocin, 15 mU of vasopressin or 50 microliter of 0.9% NaCl solution was given into the ovarian bursa over 10 min. Blood pressure and ovarian blood flow were continuously recorded. Progesterone (P) and oestradiol-17 beta (E2) were determined from the blood samples by RIA. Oxytocin did not alter the blood pressure, whereas the ovarian blood flow showed a short increasing tendency. Later, however, it started to decrease in parallel with the decrease in blood pressure owing to blood loss. The secretion of P and E2 remained unchanged. No changes in blood pressure were observed after vasopressin administration, although the ovarian blood flow quickly decreased in parallel with the secretion of P and E2. It is suggested that oxytocin has no direct effect on ovarian blood flow and hormone secretion in the rat. Vasopressin, however, is an effective vasoconstrictor in the rat ovary and may in this way reduce hormone synthesis.
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PMID:Effects of oxytocin and vasopressin on the ovarian blood flow, progesterone and oestradiol-17 beta secretion in oestrous rats. 406 Sep 75

1. In intact rats progesterone (50 mg/kg) antagonized the effect of stilboestrol (100 mug/kg) on the vaginal smears and the uterine sensitivity. The uterine sensitivity to acetylcholine, oxytocin and 5-hydroxytryptamine was decreased by 6.8, 64 and 14.8 times, respectively, as compared with uteri removed after stilboestrol injections.2. Progesterone therapy in hypophysectomized rats also antagonized the effect of stilboestrol on the vaginal mucosa and on the uterine sensitivity to drugs. The sensitivity to acetylcholine, oxytocin and 5-hydroxytryptamine was decreased by 6.2, 50 and 14.5 times, respectively. Similar results were obtained on uteri removed from sham-hypophysectomized rats.3. On the basis of these results it is suggested that the hypophysis does not play any part in the desensitization of the myometrium to the oxytocic drugs and in the changes found in the vaginal mucosa after progesterone therapy.
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PMID:Study of the effects of progesterone therapy on the stilboestrol-induced sensitivity of isolated uteri of hypophysectomized rats. 541 55

1. Progesterone treatment (50 mg/kg) in ovariectomized rats antagonizes the effects of stilboestrol 100 mug/kg on the vaginal mucosa and uterine weight; but the sensitivity to acetylcholine, oxytocin and 5-hydroxytryptamine is increased by factors 4, 11 and 3, respectively.2. In intact animals a similar progesterone treatment (50 mg/kg) antagonizes the effects of stilboestrol 100 mug/kg on vaginal smears, uterine weight and uterine sensitivity. The uterine sensitivity to acetylcholine, oxytocin and 5-hydroxytryptamine is, however, decreased by a factor of 2, 1.4 and 17.7, respectively.3. These experiments show that the ovary is essential for the desensitizing effects of progesterone. The suggestion is put forward that another substance is released from the ovary by progesterone.
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PMID:Effects of progesterone therapy on the stilboestrol-induced sensitivity of isolated rat uterus preparations. 577 46

Rats were made unilaterally pregnant by tying the right oviduct on the day after mating, to compare the oxytocin receptor concentrations in a nondistended, nonpregnant uterine horn with those in a distended, pregnant horn. On day 20, they were subjected to bilateral ovariectomy and indwelling balloons were inserted into both uterine horns. Following ovariectomy, the rats were injected im with either oil, estradiol benzoate (5 micrograms/rat per 24 h), or estradiol and progesterone together. For comparison, intact rats were studied on days 21 and 22, 24 and 48 h after insertion of the indwelling balloons. Spontaneous uterine activity and the response to increasing amounts of oxytocin were recorded 20-24 h and 44-48 h after surgery, following which the uteri were excised and assayed for oxytocin and estrogen receptors. The oxytocin receptor concentrations in the two horns were different on day 20 before the treatments were begun, the distended pregnant horn having a higher concentration per milligram DNA than the nonpregnant horn. The various treatments always changed the oxytocin receptor concentrations in the same direction; estrogen increased and progesterone inhibited the estrogen-induced rise in oxytocin receptor concentrations. In intact rats, the distention-induced increase in oxytocin receptor concentrations present on day 20 disappeared near term, but in the absence of the ovaries distention of the uterus had a significant influence on the myometrial oxytocin receptor concentrations, potentiating the effect of estrogen. Progesterone selectively inhibited the distention-induced increase in oxytocin receptor concentrations without inhibiting the hypertrophic effect of distention in general. A good correlation between oxytocin receptor numbers and tissue responsiveness was observed in all instances. The changes in spontaneous activity induced by the various treatments were distinct from the changes in oxytocin responsiveness. Estrogen exerted a strong inhibitory action on the activity stimulated by hormone withdrawal, while progesterone had no inhibitory effect. The pregnant distended horn always showed more spontaneous activity than the nonpregnant horn. There was an overall significant correlation between nuclear estrogen receptor and oxytocin receptor concentrations per milligram DNA, although the partial correlations were not significant in all groups (oil and progesterone).(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Systemic and local regulation of oxytocin receptors in the rat uterus, and their functional significance. 631 57

Prostaglandin (PG) E2 was the major PG released from the superfused guinea-pig uterus on Day 7, followed by in descending order 6-oxo-PGF1 alpha, thromboxane (TX) B2 and PGF2 alpha. However, the outputs of all four substances were low and were very similar. By Day 15, PGF2 alpha output from the superfused uterus had increased 21.9-fold, whereas the outputs of PGE2, 6-oxo-PGF1 alpha and TXB2 had increased only 1.8-, 2.9- and 1.2-fold, respectively. A mechanism is apparently "switched on" between Days 7 and 15 which causes a fairly specific increase in the release of PGF2 alpha from the uterus. Progesterone and/or estradiol had no effect on PG or TX release when superfused over the uterus on Day 7, nor did they have any effect on PG and TX release from the Day 15 uterus when administered separately. When administered together, however, they significantly inhibited PGF2 alpha, PGE2 and 6-oxo-PGF1 alpha, but not TXB2, release from the Day 15 uterus. Oxytocin had no effect on PG release from the Day 7 or Day 15 uterus, while A23187 stimulated PGF2 alpha, 6-oxo-PGF1 alpha and, to a lesser extent, PGE2 release from the uterus on both Days 7 and 15. Oxytocin is apparently not important for stimulating PGF2 alpha release from the guinea-pig uterus in relation to luteolysis, whereas increasing intracellular free Ca++ levels may be part of the mechanism for "switching on" uterine PG synthesis. Furthermore, changes in intracellular free Ca++ levels in the endometrium may be responsible for the pulsatile nature of PGF2 alpha release from the uterus.
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PMID:Prostaglandin release from the guinea-pig uterus superfused in vitro. Effect of stage of estrous cycle, progesterone, estradiol, oxytocin and A23187. 640 12

An injection of 500 micrograms prostaglandin (PG) analogue was given on Day 12 (mid-luteal phase) of the oestrous cycle to 8 cows. An LH surge occurred 59 +/- 2 h later. LH, FSH, prolactin, oestradiol-17 beta, progesterone and oxytocin concentrations were determined in blood samples collected from the caudal vena cava and/or the jugular vein at 20-min (5 cows) or 5-min (3 cows; only LH and FSH concentrations were determined) intervals for 24 h, beginning 48 h after the PG injection. Oxytocin concentrations were low and similar in the vena cava and the jugular vein. In blood samples collected every 5 min the interpulse interval for LH and FSH during the period before the LH surge was 38-40 min. In the 20-min samples the interpulse interval for oestradiol was similar to that for LH and FSH, but pulse amplitude and basal concentrations steadily increased to reach maximum concentrations 6-8 h before and again during the LH surge. A decrease in oestradiol concentrations, lasting at least 60 min, occurred just before the start of the LH surge. Progesterone concentrations also increased at the same time as the LH surge. The magnitude of the LH surges varied from 7 to 32 ng/ml, but all cows ovulated and had oestrous cycles of normal length. Distinct pulses of LH and FSH were observed throughout the LH and FSH surges. Pulsatile secretion of LH was not detected for a period of up to 6-12 h following the LH surge, but then low-amplitude pulses occurred. In contrast, the pulsatile secretion of FSH remained at a frequency similar to that observed during the descending phase of the FSH surge. Furthermore, a second increase in FSH concentrations occurred, beginning 4-12 h after the LH-surge. It is concluded that: (1) the frequent, high-amplitude pulses of oestradiol that occur before and during the LH surge are probably due to stimulation by pulses of LH; (2) the LH surge is the result of an increase in frequency and amplitude of the LH pulses; (3) the second increase in FSH that follows the LH and FSH surges appears to be the result of an increase in the amplitude (not frequency) of the FSH pulses; and (4) very little, if any, oxytocin is secreted from the ovary during the periovulatory phase of the oestrous cycle.
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PMID:Pulsatile secretion of gonadotrophins, ovarian steroids and ovarian oxytocin during the periovulatory phase of the oestrous cycle in the cow. 674 58

Bovine ovaries were obtained from the abattoir and corpora lutea were classified as: (1) early luteal phase (approximately Days 1-4); (2) mid-luteal phase (Days 5-10); (3) late luteal phase (Days 11-17); (4) regressing (Days 18-20) and (5) pregnant (Days 90-230). In addition, preovulatory follicles and whole ovaries without luteal tissue were collected. Concentrations of oxytocin, vasopressin, bovine neurophysin I and progesterone were measured in each corpus luteum by radioimmunoassay. Progesterone and neurophysin I levels increased from Stage 1 to Stage 2, plateaued during Stage 3 and declined by Stage 4. Oxytocin and vasopressin concentrations increased from Stage 1 to Stage 2 but declined during Stage 3 and were low (oxytocin) or undetectable (vasopressin) in follicles, whole ovaries and pregnancy corpora lutea. Therefore the concentrations of both peptide hormones were maximal during the first half of the cycle and declined before those of progesterone. The high concentration of oxytocin within the corpus luteum coupled with the presence of bovine neurophysin I suggests that oxytocin is synthesized locally.
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PMID:Variations in oxytocin, vasopressin and neurophysin concentrations in the bovine ovary during the oestrous cycle and pregnancy. 674 62


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