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

Slices from ox neurohypophyses were incubated in a calcium-free medium with the ionophores A23187 or X537A. X537A (5 X 10(-5) mol/l) caused a marked release of vasopressin, neurophysin and protein to the medium. A23187 (2 X 10(-5) mol/l) did not cause any release by itself, but when Ca2+ was added to the medium in the presence of the ionophore, an increase in the release of vasopressin, neuorphysin and protein occurred. Release of lactate dehydrogenase and peptidase were not affected by the ionophores. The secretion caused by A23187 was abolished by D600 (a verapamil analogue) (2 X 10(-5) mol/l) whereas the effect of X537A was unchanged. The effects of X537A were strongly inhibited by removal of sodium from the medium. Re-addition of sodium to the medium caused a marked release. Gramicidin (10(-6) or 5 X 10(-5) mol/l) had no effect on secretion. Efflux of 45Ca2+ from pre-loaded slices was drastically reduced in a sodium-free medium. X537A caused an increase in the efflux rate of 45Ca2+ both in medium with a normal concentration of sodium and when slices had been incubated in a sodium-free medium. A23187 and X537A both released 45Ca2+ from a neurohypophyseal mitochondrial fraction. When sodium in a concentration of 20 mmol/l was added to this fraction, the Ca2+ accumulation was inhibited. This effect was reduced by inorganic phosphate up to a concentration of 2 mmol/l.
Acta Endocrinol (Copenh) 1976 Sep
PMID:Calcium and stimulus secretion coupling in the neurohypophysis. V. The effects of the Ca2+ ionophores A23187 and X537 A on vasopressin release and 45Ca2+ efflux; interactions with sodium and a verapamil analogue (D600). 6 Aug 66

Myometrial activity was recorded in vivo in unrestrained pregnant rats from day 19 of gestation using radiotelemetry. The effects of short-term infusions of theophylline, dibutyryl cyclic AMP and 8-bromo-cyclic GMP were investigated. All three compounds caused a decrease in oxytocin-induced, prostaglandin F2alpha-induced and spontaneous uterine activity. After cessation of the infusion of these compounds uterine activity returned to near pre-infusion levels within approximately 15 min in most animals. The possible roles of cyclic nucleotides in the control of myometrial contraction are discussed in the light of these observations.
J Endocrinol 1975 Sep
PMID:Modification of myometrial activity in vivo by administration of cyclic nucleotides and theophylline to the pregnant rat. 17 77

A microcellular dispersion procedure for the rat neurohypophysis was developed, comprising tissue softening and dissociation using a special sieving sytringe. In preparatory studies the influence of mesh width, and treatment with trypsin, pronase or collagenase-hyaluronidase was investigated using light and electron microscopy, as well as with microchemistry by means of protein and lactate dehydrogenase activity determinations. Trypsinization gave the best results. In the final adopted procedure, 3 incubated neurohypophyses were sequentially sieved through a 200- and a 50-mum mesh. The resulting 50-mul dispersion was found to contain numerous ultrastructurally well-preserved pinched-off axonal endings (neurosecretosomes), and pituicytes often revealing processes. On the basis of DNA and oxytocin assays 11% of the pituicytes and 28% of the axonal cytoplasm were recovered. Oxytocin immunofluorescence microscopy showed hormone within the neurosecretosomes, but often also in the cytoplasm of pituicytes. Microdensity gradient centrifugation was performed on neurohypophyseal disperions, in order to obtain fractions enriched for neurosecretosomes and pituicytes. Fractions were characterized by means of phase contrast, oxytocin immunofluorescence and electron microscopy, as well as by oxytocin and DNA assays as respective markers. With a 10:14:22% (w/v) Ficoll gradient, fractions were obtained for which the relative purification was by a factor of 4 on the basis of DNA/oxytocin ratios.
Brain Res 1976 Sep 17
PMID:Enzymic preparation of neurosecretosome- and pituicyte-enriched fractions from the rat neurohypophysis. 18 63

Lactation is controlled by hormones from several endocrine glands. An undisturbed function of the anterior pituitary, of the adrenals, and of the ovaries is a prerequisite for a normal morphogenesis of the mammary gland. The epithelial ducts proliferative under the combined influence of estrogens, glucocorticoids and growth hormone, whereas the lobuloalveolar development depends on progesterone and prolactin in addition to the fore-mentioned hormones. During pregnancy pituitary prolactin may be substituted by placental lactogen. Milk synthesis begins in the second half of pregnancy. It is supported by prolactin and cortisol, which directly act on enzyme activities and processes of differentiation of the alveolar cells. The sudden surge in the secretion of milk after parturition is most likely due to the rapid decline of the serum levels of progesterone. The ejection of milk from the lactating mammary gland is controlled by a neuroendocrine reflex mechanism. Suckling is the appropriate stimulus for the release of oxytocin from the posterior pituitary. Oxytocin increases intramammary pressure by inducing contraction of the myoepithelial cells and thus aids in expelling the milk from the mammary glands. Maintenance of normal postpartum lactation depends on frequent and intensive suckling. Suckling does not only stimulate the release of oxytocin, but also provokes secretion of prolactin and ACTH. This increase in prolactin caused by suckling guarantees galactopoesis. Influencing secretion of prolactin has been proven to be a useful tool for regulating lactation. The experimental ergot derivative 2-Brom-alpha-ergocryptine is a potent suppressor of prolactin secretion from the anterior pituitary. In contrast to estrogens, alone or in combination with progestagens or androgens, this drug is not only effective in suppressing the onset of lactation, but also in inhibiting lactation once milk secretion had started. As to stimulating lactation in the human there is no effective drug available up to now.
Klin Padiatr 1976 Sep
PMID:[Hormonal regulation of lactation (author's transl)]. 18 42

In a continued effort to relate the three-dimensional structure of a peptide hormone to its biological activity, the dose-response relationships of [3-phenylalanine] oxytocin (oxypressin), with an aromatic amino acid residue in position 3, and [3-beta-cyclohexylalanine]oxytocin, with an aliphatic amino acid residue to position 3, were determined in the rat uterine assay in vitro and compared to that of oxytocin. Oxypressin has not only a lower affinity for the smooth muscle receptor than the natural hormone, but also a decreased maximal response (efficacy). [3-beta-Cyclohexylalanine]oxytocin exhibits an even lower affinity than oxypressin, but retains the same maximal response as oxytocin. A reorientation of the tyrosine sidechain, caused by the presence of a neighboring aromatic sidechain in position 3, away from the surface of the 20-membered ring is though to remove the phenolic hydroxyl group from its optimal position in the "active center" of oxytocin and give rise to the reduced efficacy of oxypressin.
Proc Natl Acad Sci U S A 1976 Sep
PMID:Importance of the third amino acid residue of oxytocin for its action on isolated rat uterus: study of relationship between hormone conformation and activity. 18 56

The respiratory distress syndrome is believed to be due to insufficient surfactant. It is known that there is a greater incidence of the respiratory distress syndrome among infants delivered by cesarean section before labor than among those delivered after labor at the same gestational age. The purpose of this study was to determine the effect of labor on the production of pulmonary surfactant. We measured the phospholipid content of lung lavage in newborn rabbits delivered by cesarean section before labor at 29, 30, and 31 (full-term) days gestation and after oxytocin-induced labor at 31 days. We also measured the activities of pulmonary cholinephosphate cytidylyltransferase and choline-phosphotransferase, enzymes involved in the de novo synthesis of phosphatidylcholine, the major component of surfactant. There was a two- to fourfold increase in the amount of lung lavage phospholipid during the first 6 h after birth. This was not dependent upon gestational age at delivery. There was a further two- to fourfold increase in the next 18 h which was, however, dependent upon gestational age. Labor increased the amount of lavage phospholipid from rabbits delivered at full term by 132%, 177%, and 50% at 3, 6, and 24 h after birth, respectively. There was a postnatal increase in the activity of cholinephosphate cytidylyltransferase. This was almost linear with time during the first 12 h, by which time essentially adult values were attained. Choline-phosphate cytidylyltransferase was not affected by labor. There was also a postnatal increase in the activity of cholinephosphotransferase but this was stimulated 86%, 59%, and 21% by labor at 0, 1, and 24 h after birth, respectively. These studies suggest that labor stimulates both the synthesis and secretion of surfactant in the immediate postnatal period and thus may be an important factor in the prevention of the respiratory distress syndrome of the newborn.
J Clin Invest 1977 Sep
PMID:Stimulation of surfactant production by oxytocin-induced labor in the rabbit. 19 22

The analysis of pA2 values for 1,2-substituted oxytocin analogues suggests a significant resonance effect of p-substituted groups in 2-tyrosine when the hormone binds to its uterus receptor, whereas the N-terminal amino group exerts less clearly characterized effects (participation of its lipophilicity and molecular volume can be assumed.
Experientia 1978 Sep 15
PMID:Affinity of 1,2-substituted oxytocin analogues to the uterus receptor: Free-Wilson and Hansch analysis. 21 32

When [35S]cysteine was injected adjacent to the supraoptic nucleus (SON) in rats, it was rapidly incorporated into proteins in the SON. The [35S]cysteine-labeled proteins extracted from the SON were separated by isoelectric focusing on polyacrylamide gels. Twenty minutes after the injection of [35S]cysteine, two major labeled peaks (pI = 5.4 and 6.1) were found in the SON of normal rats; Brattleboro rats had only one major labeled peak (pI = 5.4). One hour after the injection, four major radioactive peaks were found in the SON of normal animals (pI = 5.1, 5.4, 5.6, and 6.1). Animals with diabetes insipidus had only two major labeled proteins (pI = 5.1 AND 5.4). Twenty-four hours after normal rats were injected with [35S]cysteine, all of the labeled peaks described above, except for the one with pI = 5.1, had decreased markedly in size and a small amount of labeled protein with pI about 4.8 was present in the SON. After 24 hr the posterior pituitary of normal animals contained two [35S]cysteine-labeled proteins with pI = 4.6 AND 4.8. The pituitaries of Brattleboro rats had only the pI = 4.6 labeled protein. These pulse-chase data, with data we have presented elsewhere, indicate that the vasopressin- and oxytocin-neurophysins are synthesized as parts of separate precursors (pI = 6.1 and 5.4, respectively). These precursors are converted into at least two intermediates (pI = 5.6 and 5.1) which, in turn, yield the vasopressin-neurophysin (pI = 4.8) and the oxytocin-neurophysin (pI = 4.6).
Proc Natl Acad Sci U S A 1977 Sep
PMID:Neurophysin biosynthesis in normal rats and in rats with hereditary diabetes insipidus. 26 51

In conscious dog deamino-dicarba-oxytocin strongly stimulated a spike activity in the uterus which was more prolonged than that after oxytocin. Both oxytocin and deamino-dicarba-oxytocin inhibited the tone and peristaltic contractions of stomach and small intestines in starving dogs, eliminated the spike discharges, reduced the basic electrical rhythm frequency of the stomach and accelerated the propagation velocity of the slow waves in the small intestine. Only oxytocin, but not its deamino-analogue, reduced the pulse frequency and inhibited the spontaneous contractions of muscle strips isolated from the guinea pig stomach and portal vein.
Endocrinol Exp 1979 Sep
PMID:Effect of deamino-dicarba-oxytocin and oxytocin on myoelectrical and mechanical activity of uterus, stomach and small intestine in dog. 31 69

50 pregnant women were included in a double-blind study aimed at determining whether oral prostaglandin E2 (PGE2) can effectively prime an unripe cervix prior to oxytocin induction of labor. Study participants ranged in age from 20-37 years and were 36-41 weeks pregnant. Patients were randomly assigned to receive either PGE2 or a placebo. 2 tablets were administered at 3 hour intervals for 3 doses. Oxytocin infusion began 9-11 hours after the 3rd dose of oral medication and was increased until adequate uterine contractions were induced. No difference in the frequency of contractions was seen in the 2 groups during priming; however, PGE2 patients showed a 2 point advance in Bishop score, which was significantly greater than the 0.7 change in the control group. The most striking finding was that 6 women in the PGE2 group, compared with 1 in the placebo group, went into active labor during the priming phase and delivered without induction. Oxytocin failed to induce effective labor in 9 patients in each group. There was no difference between the 15 control and 10 PGE2 patients successfully induced in terms of duration or dosage of oxytocin. However, the more inducible patients in the PGE2 group may have begun labor before oxytocin induction, rendering the groups less equivalent for the induction part of the study. These results suggest that oral PGE2 priming results in an easier course to delivery, although not in a higher incidence of successful induction. It is recommended that the PGE2-oxytocin induction regimen be studied in patients at various stages of induction, perhaps with an increased dosage of PGE2 or a shorter interval between dosages.
Prostaglandins 1977 Sep
PMID:Uterine priming with oral prostaglandin E2 prior to elective induction with oxytocin. 33 16


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