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

Prolactin, as a "broad spectrum hormone", has been described to exert also vascular and renal actions in laboratory animals and in humans. However, prolactin preparations of various species are contaminated with neurohypophysial hormones (ADH, oxytocin) which possess vascular and renal activities. Antisera against ADH, oxytocin and prolactin are rather specific inactivators of the biologic activity of the respective hormone; the oxytocinasevasopressinase system of pregnancy plasma destroys ADH and oxytocin. Incubation-identification procedures with antisera against ADH, oxytocin and prolactin and with pregnancy plasma revealed that changes in blood pressure, urine flow and urinary osmolarity cannot be ascribed to prolactin per se but to the ADH impurity of prolactin preparations. Furthermore, recent metabolic studies in normally hydrated, overhydrate and dehydrated animals and humans have shown that prolactin does not affect renal water and electrolyte excretion. Thus, earlier reports on vascular and renal activity of prolactin in laboratory animals and humans should be viewed with great caution. Elimination of neurohypophysial hormone impurities of prolactin preparations by incubation with either ADH and oxytocin antisera or with pregnancy plasma provides techniques for better assessment of the real biologic effects of the prolactin molecule.
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PMID:Renal and vascular activity of prolactin preparations. Contamination of prolactin preparations with ADH and implications on renal and vascular prolactin research. 43 76

The effects of prolactin and other hormones applied electrophoretically to 400 neurons in the brain were studied in rats under urethane anesthesia. 51 prolactinactivated neurons were distributed mainly in the nucleus dorsomedialis, the upper part of the nucleus ventromedialis, and the nucleus habenulae. 26 prolactin-inhibited neurons were diffusely distributed from the nucleus arcuatus to the zona incerta. Prolactin failed to affect the neurons of the cerebral cortex. Almost all units recorded in the preoptic and lateral hypothalamic areas were not affected. About half of both prolactin-activated and -inhibited neurons were suppressed by estrogen and betamethasone but were not affected by either oxytocin or thyrotropin releasing hormone. This study affords direct evidence for the presence of prolactin-sensitive neurons in the hypothalamus.
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PMID:Effects of iontophoretically-applied prolactin on unit activity of the rat brain. 81 Jul 35

Mammary glands of rats on day 14 of lactation were emptied of milk by the pups after 8 h of nonsuckling with the aid of oxytocin injections to the mother. The glands subsequently refilled about 50% within 6 h and were completely refilled with mild within 16 h. Suckling for 5 min midway during the 8 h period of nonsuckling caused complete refilling of the glands within 6 h. Refilling within 6 h also occurred if, instead of suckling, rat prolactin was injected at 1 min intervals directly into the circulation of the conscious mother via an indwelling right atrial catheter. Five injections of 200 ng or three injections of 400 ng were without effect (in comparison with five injections of saline) upon mammary refilling whereas 10 injections of 200 ng or four injections of 400 ng simulated significant but submaximal refilling. Complete refilling resulted from five injections of 400 ng. Prolactin is secreted steadily over prolonged periods of suckling in the rat, but only that prolactin released during the first few minutes of suckling appears to be required for milk secretion.
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PMID:Milk secretory response of the conscious lactating rat following intravenous injections of rat prolactin. 120 34

The effects of prolactin or oxytocin on milk secretion and the permeability of the mammary epithelium have been investigated in rabbits. 2. Milk yield was increased by prolactin treatment in late (25-28 days) but not in established (11-14 days) lactation. 3. Prolactin treatment increased milk [lactose] and [K] and decreased [Na] and [Cl] in late lactation, and thus reversed the normal changes in late lactation, but had no significant effect in established lactation. 4. [14C]sucrose movements from blood to milk were significantly decreased to levels characteristic of established lactation, following prolactin treatment in late lactation. No significant effect was evident with treatment in established lactation. Na and Cl movements showed similar trends. 5. It is suggested that prolactin in some way affects paracellular movements of ions and small molecules like lactose across the mammary epithelium, and that this mechanism is responsible for the changes in the composition of the aqueous phase of milk. 6. Immediately following a single dose of 100 m-u. oxytocin no significant effects on milk composition were evident but after 1 u. milk [Na] and [cl] were significantly increased. 7. Twenty-four hr after 1 u. oxytocin, milk [Na] and [cl] were decreased while [K], [lactose], [fat] and [protein] were increased. 8. During an I.V. infusion of oxytocin milk [Na] and [Cl] increased while [K] and [lactose] decreased. The passage of [(14)C]sucrose, 24Na and (36)Cl from blood to milk also increased. 9. These effects of oxytocin are discussed in relation to the permeability of the mammary epithelium and the pathways for ion movements, and to other studies on milk composition in the rabbit involving the administration of oxytocin to aid in the evacuation of milk.
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PMID:The effects of prolactin and oxytocin on milk secretion and on the permeability of the mammary epithelium in the rabbit. 121 26

There is a great variation in body weight loss during lactation among primiparous sows fed a standard diet that is adjusted based on the number of piglets nursed and the maintenance requirements. Energy and protein catabolism is more pronounced during the first 1 to 3 weeks of lactation and sows with low weight loss recover earlier from their negative energy balance during lactation than sows with high weight loss. Using continuous blood collection a decrease in plasma levels of oxytocin, prolactin, and insulin, and an increase in plasma levels and no of LH pulses during lactation were demonstrated. Prolactin levels gradually increased in response to each suckling while only 40-50% of recorded sucklings induced a significant rise in plasma oxytocin. Following a 24-h fast during lactation, levels of prolactin were very low but increased rapidly after refeeding. Even plasma levels of insulin and glucose decreased to very low levels during fasting, but the release of LH was similar before and after refeeding. Weaning resulted in decrease in plasma levels of prolactin and increase in plasma levels and no. of LH pulses. Plasma levels of cortisol showed a diurnal pattern of change which disappeared on the day of weaning. In response to weaning plasma levels of glucagon and gastrin decreased, whereas insulin and somatostatin increased. At weaning sows with low weight loss during lactation had higher plasma insulin and lower plasma cortisol levels than sows with high weight loss, but no differences in levels or no. of LH pulses were observed between the two groups of sows.
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PMID:Metabolic and reproductive hormones during lactation and the post-weaning period in sows. 134 70

Neuropeptides that may induce behavioral activation--thyrotropin-releasing hormone (TRH), oxytocin (OXY), and prolactin (PRL)--were tested on thiopenthal-induced narcosis after IV administration in male rats. TRH caused a significant shortening of sleeping time at the doses of 3 and 5 mg/kg, but did not change this parameter at lower doses. Oxytocin was effective at all doses tested (200, 300, and 400 micrograms/kg). Prolactin also shortened sleeping time at the doses of 0.2 and 1 mg/kg administered IV, slightly increasing it at the dose of 5 mg/kg. These results indicate that various neuropeptides are capable of reducing the duration of thiopenthal-induced sleep in rats.
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PMID:Effects of thyrotropin-releasing hormone, oxytocin, and prolactin on thiopenthal-induced narcosis in rats. 161 61

In 117 parturients with 38-41 gestation weeks, prolactin was analysed by the radioimmunologic method in the mother serum, the umbilical cord serum and vein, and in the amnionic fluid. Three groups of parturients and their newborns were examined: the group (n = 44) with the birth having started spontaneously with the appearance of labour pains 1/10 minutes, the group (n = 38) with a programmed birth induced by the infusion of oxytocin, and the group (n = 35) with the birth comprising elective cesarean section. The concentration of prolactin in the examined sera is characterized by considerable individual oscillations. The highest prolactin level was in the amnionic fluid (395.6 +/- 130.1 mu/L) and the lowest in the mother serum (174.6 +/- 84.1 mu/L) which shows a statistically significant difference (p less than 0.01). Prolactin values in the umbilical artery (244.6 +/- 98.3 mu/L) and vein (230.4 +/- 91.7 mu/L) are significantly (p less than 0.001) higher than the value in the mother sera and significantly lower (p less than 0.001) than the prolactin concentration in the amnionic fluid. The difference of the prolactin values in the sera of the umbilical cord blood vessels has no statistical significance (p greater than 0.05). Nor is there any statistically significant difference between prolactin concentrations in spontaneous and induced deliveries versus those in deliveries terminated with elective cesarean section (p greater than 0.05). A correlation analysis of the functional connection of prolactin in the sera of the mother, fetus, and amnionic fluid gives the correlation coefficient values of high statistical significance (0.482 less than r less than 0.906; p less than 0.001).
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PMID:[Correlation between levels of prolactin in maternal serum, fetal serum and amniotic fluid in childbirth at term]. 174 78

Circulating concentrations of 13,14-dihydro-15-keto PGF2 alpha (DHKF2 alpha), luteinizing hormone (LH) and prolactin (PRL) have been measured in cyclic ewes treated with continuous infusions of oxytocin, in order to investigate the mechanism by which the treatment delays luteal regression. Continuous infusion of oxytocin reduced prostaglandin F2 alpha (PGF2 alpha) secretion but had no detectable direct effect on LH or PRL. Oxytocin (3 nmol h-1 i.v.) given from Day 12 or 13 until Day 18 after oestrus delayed luteolysis, eight out of nine treated ewes not returning to behavioural oestrus until Day 29.1 +/- 3.2 (mean +/- s.e.m.; cycle length of control ewes 16.7 +/- 0.3 days). In the ewe in which oxytocin failed to prevent luteolysis, luteal regression had commenced before oxytocin treatment was started. In three ewes undergoing delayed luteolysis (cycle lengths, 21, 24 and 25 days) basal concentrations of PGF2 alpha (measured as DHKF2 alpha) were unchanged, but there was only one episode of PGF2 alpha secretion compared with 20 episodes in three control ewes. Prolactin secretion was pulsatile during oxytocin infusion, and levels were low following infusion in ewes with cycle length greater than 25 days while the corpora lutea were maintained. Circulating PRL concentrations were high in ewes undergoing delayed luteolysis but there was not discrete episode of PRL secretion associated with the pre-ovulatory LH surge in these animals. To investigate the possibility that the pattern of PGF2 alpha secretion was affected by depletion of oxytocin from corpora lutea, ewes previously treated with oxytocin to delay luteolysis were given a luteolytic dose of cloprostenol on Day 21 after oestrus. The amount of oxytocin secreted in response to cloprostenol was less than 10% of that seen in ewes similarly treated on Days 11-13 after oestrus. Low levels of luteal oxytocin may therefore reduce PGF2 alpha secretion in ewes undergoing delayed luteolysis.
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PMID:Effect of continuous infusion of oxytocin on prostaglandin F2 alpha secretion and luteolysis in the cyclic ewe. 233 92

Studies were undertaken to investigate the effects of oxytocin induction on prolactin release in term (Group II) and preterm (Group III) mares and to compare these effects to spontaneously foaling mares (Group I). Since physiological concentrations of prolactin in blood have not been measured in the neonatal foal, experiments were designed to monitor prolactin in the cord artery and jugular blood of the foals from all groups of mares. Although prolactin levels varied in term mares (Group I and II) during the last 11 days of pregnancy, an increase was observed between Day -6 and Day 0 (2.7 and 11.9 ng/ml respectively; P less than 0.1). The average concentration of prolactin over the last 4 days (Days -3 to 0) had increased by 40% when compared to the average concentration on Days -6, -5, and -4. These findings indicate a rising trend which appears to occur concomitantly with changes in concentrations of 2 mammary components tested, sodium and potassium. Prolactin concentrations did not significantly increase in term mares after oxytocin treatment or in spontaneously foaling mares. However, the preterm induced mares had higher prolactin concentrations during the first stage of labor (19.3 +/- 7.2 ng/ml) than prior to treatment with oxytocin (4.7 +/- 2.0 ng/ml; P less than 0.01). Levels of prolactin in all groups significantly declined by 20-min post-placental expulsion. For the first 30 min after birth, prolactin concentrations in foals from oxytocin-induced mares appeared to be 2-fold higher than those from spontaneously foaling mares. Thereafter, prolactin values declined to baseline values by 48 hrs. When comparing cord arterial plasma with cord venous plasma in each group, prolactin concentrations were similar. However, the average prolactin levels in both the cord artery and vein appeared higher (ave: 1.1 ng/ml) in Group II and III than in Group I (less than 0.5 ng/ml). From these results, the authors suggest that 1) prolactin may have a role in regulating mammary secretory products in mares just prior to parturition; 2) oxytocin may increase prolactin secretion in preterm induced mares; 3) oxytocin induction may have a short term effect to increase circulatory prolactin concentrations in neonates in utero regardless whether their dams were treated preterm or term.
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PMID:Plasma prolactin concentrations in mares and their neonates after oxytocin induction of parturition. 273 12

Blood samples were collected from 8 lactating sows every 2 h for 24 h periods on the Days 5, 10, 15, 20, 25, 30 and 35 of lactation. Additional samples were drawn from four sows during morning spontaneous sucklings on the same days. Prolactin (PRL), oxytocin (OT), estradiol 17-beta (E2) and estrone (E1) were measured by RIA. Corticosteroids (CS) were determined by competitive protein binding assay (CPBA). In 4 of 8 sows, elevated concentrations of PRL were concomitant with greater concentrations of CS and slightly larger concentrations of OT. Mean concentrations of E1 were markedly greater than those of E2 in 6 of 8 sows. A response of PRL to nursing was observed in 90% of all suckling events studied. A CS increase was observed in 64% of suckling occurrences. During suckling OT surges appeared with peripheral concentrations greater on day 5 and 10 of lactation versus days 15, 20, 25, 30 and 35.
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PMID:Hormonal changes during lactation in sows: influence of spontaneous suckling on prolactin, oxytocin and corticoids concentrations. 273 44


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