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)

The sarcolemma of smooth-muscle cells from human pregnant myometrium possesses a high-affinity Ca2+-ATPase, which has the characteristics of an active Ca2+-extrusion pump. This pump enzyme, either membrane-bound or solubilized, was strongly inhibited by oxytocin (half-maximal inhibition at about 4 microU/ml or 10 pM). However, under similar conditions, oxytocin did not inhibit Ca2+-extrusion ATPase of the erythrocyte membrane. The inhibitory concentrations of oxytocin correspond to hormone plasma levels which initiate spontaneous labor.
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PMID:Oxytocin contracts the human uterus at term by inhibiting the myometrial Ca2+-extrusion pump. 315 10

1. The intracellular (I.C.) concentrations of Na, K and Cl in mammary cells from lactating guinea-pigs have been calculated from the analysis of fresh tissue and the measurement of the extracellular (E.C.) space with [(14)C]sucrose and the milk content with [(14)C]lactose.2. Assuming that alveolar milk has the same concentration as teat milk, the intracellular concentrations were calculated to be K 115, Na 42 and Cl 66 m-equiv. l(-1) intracellular water.3. Intracellular concentrations were also calculated in slices incubated in Krebs-bicarbonate medium plus glucose. There was a large increase in the sucrose (E.C.) space and a rise in total tissue [Na] and [Cl]. On the assumption that the medium had equilibrated with the milk space as well as the E.C. space, the calculated I.C. concentrations of Na (43 m-equiv. l(-1)), and Cl (62) were very similar while [K] was somewhat higher (143 m-equiv. l(-1)I.C. water).4. The calculated I.C. concentrations of all three ions are all higher than in milk but the ratios between them are almost identical.5. Similar figures for the I.C. concentrations of Na, K and Cl have been obtained in the goat, cow and sheep mammary tissue incubated in vitro.6. Moderate changes in the concentrations of Na, K and Cl in the external medium had no effect on cell composition but during incubation without ions [(14)C]sucrose became distributed throughout the total tissue water indicating that sucrose had entered the I.C. compartment.7. Acetazolamide (10(-2)M), aldosterone (1.4 x 10(-6)M) and, in some experiments, lack of glucose lowered I.C. [Cl(-)], but oxytocin, vasopressin and low doses of insulin had no effect.8. The data are difficult to reconcile with the hypothesis of Zaks, Natochin, Sokolova, Tanasiichuk & Tverskoi (1965) that freshly secreted milk has the ionic composition of plasma.9. Comparison of I.C. ion concentrations and the membrane potential between the cells and milk suggests that Na(+) and K(+) are passively distributed across the apical membrane but that Cl(-) must be actively held in the cells. Across the basal membrane the data are consistent with the presence of a Na(+) pump and with Kinura's (1969) detection of a Na:K ATPase on the basal and lateral membranes. In addition another inward-facing Cl(-) pump may exist at this site.
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PMID:Intracellular concentrations of sodium, potassium and chloride in the lactating mammary gland and their relation to the secretory mechanism. 510 48

Preparations of rabbit small intestine smooth muscle cell sarcolemma are capable of hydrolyzing ATP in the presence of millimolar concentrations of Mg2+ and Ca2+ and possess the activity of Mg2+,Ca2+-ATPase having a high affinity for Ca2+ (Km = 5.8 X 10(-6) M). The optimal conditions for the Mg2+,Ca2+-ATPase reaction were established. It was demonstrated that sarcolemmal preparations hydrolyze ATP, GTP, ITP and UTP almost at the same rates. The enzyme contains SH-groups that are unequally exposed to the water phase and are inhibited by 50% by p-chloromercurybenzoate and by 90% by dithionitrobenzoate. The Mg2+,Ca2+-ATPase activity is highly sensitive to oxytocin: at the concentration of 10(-7) MU/ml, the hormone completely inhibits the enzyme without affecting its Mg2+-, Ca2+- and Na+,K+-ATPase activities.
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PMID:[Mg2,Ca2+-ATPase activity of sarcolemmas of intestinal smooth muscle cells in the rabbit]. 615 2

Changes in shape and volume of mammary secretory cells and in their RNA content, under the action of oxytocin, are considered. Under ouabain suppression of Na,K-ATPase activity, no swelling or shape changes occur in the secretory cells, in addition to no increase in their RNA content, which is characteristic of the cell reaction during the initial period of oxytocin action.
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PMID:[Changes in mammary secretory epithelial reactions to oxytocin action under the influence of ouabain]. 616 37

Myoepithelial and secretory cells from the mammary gland of the lactating rat have been isolated, purified, and characterized. Mammary tissue was dissociated with collagenase into basket-like networks of myoepithelial cells and single secretory cells. Because of their larger size, the myoepithelial cell networks could be separated from other mammary and blood cells by differential centrifugation. Isolated secretory cells were purified by isopycnic centrifugation in 25% bovine serum albumin. The purified myoepithelial and secretory cells were viable, as shown by the incorporation of 32P into distinct macromolecules that were separable by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Both myoepithelial and secretory cells retained their characteristic morphology after isolation and purification, as shown by light, transmission, and scanning electron microscopies. The isolated myoepithelial cells were unique and, thus, distinguishable from other mammary cells in a number of respects; they 1) contracted in response to the addition of oxytocin, 2) bound [3H]oxytocin specifically, 3) accounted for the content of alkaline phosphatase and [Na+ + K+]ATPase in mammary tissue, and 4) reacted specifically with antiserum prepared against purified myoepithelial cells. The purified secretory cells were unique in possessing glucose-6-phosphate dehydrogenase activity. The different cell markers not only gave independent estimates of the purity of the cell fractions, but they also may be helpful in identifying mammary cells in stages of differentiation and neoplastic transformation.
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PMID:Purification and characterization of mammary myoepithelial and secretory cells from the lactating rat. 624 56

An endogenous inhibitor of the Na,K pump, postulated to be involved in the etiology of some hypertensive states, has been reported in extracts of mammalian brain. This encouraged us to test its effects on arterial muscles. An acid-acetone extract of guinea pig brain inhibited Na,K-ATPase derived from canine kidney and evoked responses in arterial strips similar to those produced by ouabain. Unlike ouabain, however, it did not prevent muscles in K-free solutions from relaxing when K was re-added. Bioassays on strips of arteries, uterus and portal vein indicated that the extract did not contain sufficient concentrations of norepinephrine, dopamine, serotonin, prostaglandins, angiotensin II, oxytocin or the Na,K-ATPase inhibitor to account for the observed vascular effects. This could not be said of vasopressin. Furthermore, vasopressin and the vasoactive component of the extract were equally sensitive to several peptidases, and conditions which cleave disulfide bridges. A radioimmunoassay verified that the extract contained sufficient vasopressin to cause contractions. Vasopressin did not inhibit the kidney Na,K-ATPase activity. Finally, the Na,K-ATPase inhibitor, but not the vasoactive substance, was present in extracts of vasopressin-deficient Brattleboro rat brains. Therefore, the Na,K-ATPase inhibitor and the vasoactive substance in these extracts were distinctly different.
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PMID:Identification of a vasoactive substance (vasopressin) in a brain extract containing an unknown inhibitor of Na,K-ATPase. 626 68

A new potent vasodilator, nicardipine hydrochloride inhibited oxytocin-induced contraction of rat uterus dose-dependently with an increase in the intracellular cyclic AMP level at the onset of relaxation. Dibutyryl cyclic AMP and papaverine, an inhibitor of cyclic AMP phosphodiesterase (PDEase), also inhibited the contraction. Nicardipine inhibited competitively PDEase in homogenates of rat uterus which exhibited apparently two Km values for cyclic AMP (3.6 micro M and 67.3 micro M) with the Ki of 5.3 micro M and 13.2 micro M, respectively, but had no effect on adenylate cyclase. Nicardipine enhanced calcium uptake by rat uterine microsomes, at concentrations which inhibited oxytocin-induced contraction in the same manner as cyclic AMP. The maximal stimulation by nicardipine of the microsomal calcium uptake was identical substantially to that by cyclic AMP, and both were not additive. Cyclic AMP was also accumulated during the uptake reaction in the presence of nicardipine. On the contrary, neither myosin ATPase nor microsomal Ca2+-dependent ATPase was inhibited directly by nicardipine. These results suggest that the inhibition of oxytocin-induced contraction of rat uterus by nicardipine may be due to an enhancement of microsomal calcium uptake, mediated by cyclic AMP accumulated through the inhibition of PDEase.
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PMID:A possible mechanism for relaxation of rat uterine smooth muscle by nicardipine hydrochloride (YC-93), a new potent vasodilator. 627 30

1. Ouabain-sensitive 86Rb+ uptake in slices of lactating rabbit mammary gland significantly increased after 20 min or 1 hr of incubation with ovine prolactin (NIH-P-S12; 1 microgram/ml.). 2. Total K+ content of the tissue significantly increased at 20 min of incubation with prolactin. 3. Neither vasopressin nor oxytocin, at concentrations of 2,20 or 40 mui.u./ml., had a significant effect on ouabain-sensitive 86Rb+ uptake or total K+ of the tissue after 30 min or 1 hr of incubation. 4. Tissue slices incubated in cycloheximide at 10 micrograms/ml. for up to 260 min showed a reduction in ouabain-sensitive 86Rb+ uptake and total K+ content, with half-lives of 115 and 63 min, respectively. 5. No consistent in vitro effect of prolactin on (Na+ + K+)-activated ATPase activity in homogenates, crude microsomal fractions or NaI-activated membrane fractions from lactating rabbit mammary gland was found. 6. After 3 hr of incubation of tissue slices in the presence or absence of prolactin (5 micrograms/ml.), no significant differences in the number of [G-3H]ouabain molecules bound per cell (5.2 X 10(4) and 6.2 X 10(4), respectively) or in the dissociation constant (KD) for ouabain binding (5.4 X 10(-7) M and 5.9 X 10(-7) M, respectively) were observed. 7. Incubation of the tissue with cycloheximide (10 micrograms/ml.) for 1-6 hr caused an exponential decrease in [G-3H]ouabain binding with a half-life of 3 hr. 8. It is concluded that prolactin stimulates the activity of the (Na+ + K+)-activated ATPase in slices of lactating rabbit mammary gland within one hour but over this period does not affect the number of ouabain-binding sites, which are apparently turned over with a half-life of 1-3 hr.
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PMID:Effect of prolactin on 86Rb+ uptake, potassium content and [G-3H]ouabain binding of lactating rabbit mammary tissue. 630 27

Total and Na+, K+-ATPase activities have been measured in sections (10 micron thick) from blocks of rat kidney cultured for 5 h at 37 degrees C, pH 7.5, in Glasgow Eagle's Minimum Essential Medium. Synthetic [arginine]vasopressin [( Arg]VP) stimulated ATPase activity in the thick tubular cells of the renal outer medulla over the concentration range 0.01-10 fmol/l, but failed to affect ATPase activity in the proximal and distal convoluted tubules of the cortex. The increase in medullary total ATPase activity induced by [Arg]VP and its analogues was wholly due to stimulation of Na+, K+-ATPase activity. Stimulation of medullary ATPase activity was blocked by [Arg]VP antiserum. The [Arg]VP analogues desmopressin, [lysine]vasopressin, [arginine]vasotocin and oxytocin stimulated medullary Na+, K+-ATPase activity, the three last-named analogues being considerably less potent than [Arg]VP.
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PMID:The stimulation of Na+, K+-ATPase activity in the medulla of the rat kidney by [arginine] vasopressin and its analogues. 632 92

Phasic myometrial contractions utilize mechanisms involving the cycling of calcium into and out of intracellular calcium stores. These studies were performed to determine the effects of 2,5-di(tert-butyl)-1,4-hydroquinone (tBHQ), an endoplasmic reticulum Ca(2+)-ATPase inhibitor, on in vitro isometric myometrial contractions. These studies demonstrated that low concentrations of tBHQ (eg. 10 microM) appear to inhibit intracellular calcium cycling, whereas higher concentrations also inhibit extracellular calcium influx. These combined tBHQ effects markedly suppressed myometrial contractions stimulated in response to various agonists including oxytocin, PGF2 alpha, KCl, ionomycin, and Bay K 8644.
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PMID:Effects of 2,5-di(tert-butyl)-1,4-hydroquinone, an endoplasmic reticulum Ca(2+)-ATPase inhibitor, on agonist-stimulated phasic myometrial contractions. 753 6


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