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Query: UNIPROT:P01185 (vasopressin)
 23,126 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Intracellular recordings were made from sympathetic preganglionic neurones (SPNs) in transverse slices of thoraco-lumbar spinal cord of young rats (12-20 days old). A small group of SPNs generally having higher membrane potentials (-70 mV) compared to a remaining group (-66 mV) showed spontaneous oscillations of their membrane potential. Oxytocin superfused in concentrations of 0.1-30 microM had four effects on SPNs, inducing slow depolarisation, EPSPs, IPSPs and brief rhythmic oscillations. The slow depolarisation was unaffected by TTX whereas this abolished the other changes. The oxytocin-induced depolarisation was associated with a slow inward current and was not reversed at membrane potentials negative to EK, it increased at more positive potentials and was still present in low Ca2+ and high Mg2+ solutions. These features of the oxytocin induced current are similar to those of the TTX resistant voltage dependent Na+ current described in brainstem autonomic neurones. Vasopressin superfused at concentrations of 0.1 microM to 30 microM had similar effects on SPNs to those of oxytocin. A comparison of the effects of oxytocin and vasopressin on the same neurones revealed that oxytocin was almost 10 times less potent than vasopressin. The effects of oxytocin were not mimicked by a selective oxytocin agonist but were mimicked by a selective vasopressin V1a agonist and blocked by a selective V1a antagonist. Therefore it is concluded that the effects of oxytocin on SPNs are mediated by the vasopressin V1a receptor. It is suggested that oxytocin and vasopressin terminals in the lateral horn are part of a descending system controlling oscillating networks of SPNs in the spinal cord.
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PMID:Oxytocin acts at V1 receptors to excite sympathetic preganglionic neurones in neonate rat spinal cord in vitro. 792 7

Magnesium transport across the plasma membrane of cardiac and liver cells appears to be under hormonal control. The increase in cytosolic cAMP, following the adrenergic stimulation of both cell types, results in a major Mg2+ efflux from perfused rat hearts or livers and from collagenase-dispersed ventricular myocytes or hepatocytes. By contrast, the activation of protein kinase C by carbachol, vasopressin, phorbol-myristate acetate or diacylglycerol analogs induces Mg2+ accumulation in either of the experimental models. As for the role of intracellular compartments on Mg2+ homeostasis, the cAMP-mediated Mg2+ efflux largely depends on the mobilization of Mg2+ from mitochondria via the mitochondrial adenine nucleotide translocase. By contrast, Mg2+ influx appears to be related to the endo(sarco)plasmic reticulum and its dynamic handling of cytosolic Ca2+.
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PMID:Cell magnesium transport and homeostasis: role of intracellular compartments. 826 15

Collagenase dispersed rat liver hepatocytes release Mg2+ when stimulated with norepinephrine or accumulate Mg2+ when stimulated with vasopressin, respectively. Mg2+ fluxes in either direction account for a net loss or gain of approximately 10% of total cell magnesium and are rapidly reversible. Both stimulated Mg2+ efflux and Mg2+ influx require physiological concentration of extracellular NaCl and Ca2+. In the absence of extracellular Na+, Mg2+ efflux, but not influx, can be observed in the presence of extracellular Cl-. Under these conditions, the efflux is inhibited by the Cl-/HCO3- exchanger inhibitor 4,4'-dinitrostilbene-2,2'-disulfonic acid. In hepatocytes, Mg2+ influx, but not efflux, is completely inhibited by thapsigargin, a specific inhibitor of the endoplasmic reticulum Ca2+ ATPase. Several lines of evidence, such as measurements of cytosolic Ca2+ or of cytosolic Ca2+ buffering, indicate that the effect of thapsigargin in inhibiting Mg2+ influx could not be explained by an increase in cytosolic Ca2+. Instead, the inhibition of hepatocyte Mg2+ influx was found to be the result of the depletion of the Ca2+ stored within the endoplasmic reticulum.
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PMID:Hormonal stimulation of Mg2+ uptake in hepatocytes. Regulation by plasma membrane and intracellular organelles. 834 Mar 77

We have characterized a specific binding site for angiotensin IV on bovine aortic endothelial cell membranes. Pseudo-equilibrium studies at 37 degrees C for 2 h have shown that this binding site recognizes angiotensin IV with a high affinity (Kd = 0.71; average of two experiments that yielded values of 0.71 and 0.72 nM). The binding site is saturable and relatively abundant with a maximal binding capacity of 0.59 pmol/mg protein (average of two experiments that yielded values of 0.39 and 0.78 pmol/mg of protein). Non-equilibrium kinetic analyses at 37 degree C revealed a calculated Kd of 59 pM (average of two experiments that yielded values of 67 and 50 pM). The binding site displays a high affinity for angiotensin receptors AT1 or AT2. An analysis of specificity showed that the binding site displays a high affinity for angiotensin IV, low affinities for angiotensin II, [Sar1, Val5, Ala8]angiotensin II and does not recognize L-158,809 (5,7-dimethyl-2-ethyl-3-[(2'-(1 H-tetrazole-5-yl)[1,1'-biphenyl]-4-yl)methyl]-3H-imidazo[4, 5-beta]pyridine H2O) and PD 123319 (1-[4-dimethylamino)3-methylphenyl]methyl-5-(diphenylacetyl) 4,5,6,7-tetrahydro-1 H-imidazo[4,5-c]pyridine-6-carboxylic acid). A few unrelated hormones (bradykinin, [Arg8] vasopressin, endothelin-1, atrial natriuretic factor, isoproterenol and adrenocorticotropic hormone) were unable to inhibit any 125I-angiotensin IV binding. The affinities of different structural analogues of angiotensin IV revealed that the N-terminal position is critical for receptor recognition and the C-terminal proline is also important. GTP gamma S and polyvinyl sulfate did not affect the binding, suggesting that the receptor is not coupled to a G-protein. The divalent cations Mg2+ and Ca2+ were shown to diminish the binding of 125I-angiotensin IV. Cross-linking of 125I-angiotensin IV to bovine aortic endothelial cell membranes in the presence of disuccinimidyl suberate, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed a major band of 186 +/- 12 kDa. The presence in high concentration of this angiotensin binding site on aortic endothelial cells suggest the existence of a novel mechanism involved in the control of vascular tone or vascular permeability.
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PMID:Characterization of a binding site for angiotensin IV on bovine aortic endothelial cells. 856 70

In the early distal tubule of the newt Triturus vulgaris L., 1 nM arginine-vasopressin (AVP) increased water reabsorption; the fractional reabsorption of Na+ was elevated from 46.2 +/- 6.9% to 67.8 +/- 3.9% (P < 0.001), of Cl- from 52.7 +/- 6.7% to 73.1 +/- 3.5% (P < 0.001), of Mg2+ from 48.0 +/- 7.7% to 71.7 +/- 6.3% (P < 0.001). When V1-receptors were blocked by 1 nM peptide V1-antagonist [1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid), 2-(O-methyl) Tyr]-[Arg8]vasopressin, 1 nM AVP increased the fractional reabsorption of fluid by 8.9% of Na+ by 10.7% and of Cl- by 11.2%, as compared with the effect of AVP alone. The fractional reabsorption of Ca2+ after addition of AVP did not differ from control; when V1-receptors were blocked in the presence of AVP, the fractional reabsorption of Ca2+ was increased by AVP. The V1-receptor block in the presence of AVP did not change the fractional reabsorption of Mg2+. Experiments on the urinary bladder of the frog Rana temporaria L. showed that 1 nM SR 49059, a non-peptide antagonist of V1a-receptors, like the peptide V1-antagonist, enhanced the AVP effect by 29%. Inhibition of protein kinase C activity by calphostin C (1 nM) mimicked the effect of V1-antagonists; the AVP hydroosmotic effect was increased by 60%. The results obtained indicate that V1-receptors modulate the effects of V2-receptor activation: their block is accompanied by an enhancement of the AVP hydroosmotic effect in the frog urinary bladder and by an increase of Na+ and Cl- reabsorption in the newt early distal tubule. The enhancement of the AVP effect owing to the V1-receptor activation seems to be mediated by a decrease in protein kinase C activity.
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PMID:Modulation of the effect of arginine-vasopressin on water and ion transport in the newt early distal tubule and frog urinary bladder by V1-antagonists. 859 34

Several metal ions are known to cause depolymerization of the actin cytoskeleton under some circumstances. We found that in renal mesangial and vascular smooth muscle cells, micromolar concentrations of Cd2+ result in loss of phalloidinstainable filamentous (F-) actin. The decrease in F-actin was not accompanied by a corresponding increase in G-actin. The decrease in total actin could be accounted for in part by an inhibition by Cd2+ of total protein (and actin) synthesis after 6 to 8 h without an effect on actin degradation, and the equilibrium between F- and G-actin was shifted to maintain near-constant levels of G-actin. However, Cd2+ caused significant decreases in F-actin at earlier times, indicating effects on the polymerization equilibrium independent of those on actin synthesis. Only picomolar concentrations of free intracellular Cd2+ occur in these experiments. However, it is this Cd2+ pool which is responsible for F-actin depolymerization because equal cellular concentrations of cadmium delivered as Cd-metallothionein have no effect. The effect is also very specific for Cd2+ and under the same conditions neither Mg2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, nor Hg2+ result in any loss of F-actin. Addition of Cd2+ to mesangial and vascular smooth muscle cells had no immediate effect on free intracellular calcium concentrations ([Ca2+]i) even though Ca(2+)-signalling pathways were intact as shown with vasopressin and endothelin. Exposure to 10 microM CdCl2 for 8 h nevertheless caused an increase in [Ca2+]i to > 250 nM and increases in [Ca2+]i achieved with ionophores alone were sufficient to decrease F-actin concentrations. However, a rise in [Ca2+]i is not necessary for actin depolymerization. Depletion of cellular Ca2+ by treatment with thapsigargin did not protect F-actin against Cd2+; the effect of Cd2+ was enhanced in cells unable to increase their [Ca2+]i. We conclude that depolymerization of F-actin by Cd2+ in smooth muscle and mesangial cells is metal-specific, Ca(2+)-independent, and accompanied by a depletion of total actin protein.
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PMID:Calcium-independent effects of cadmium on actin assembly in mesangial and vascular smooth muscle cells. 867 40

Vasoactive peptides mobilize cytosolic free Mg2+ in vascular smooth muscle cells. It is unknown whether angiotensin II and arginine vasopressin, potent vasoconstrictor agents, influence intracellular Mg2+. The effects of angiotensin II and vasopressin on intracellular free Mg2+ concentrations ([Mg2+]i) were therefore investigated in primary cultured unpassaged vascular smooth muscle cells (VSMC) from mesenteric arteries of Wistar Kyoto rats, and in an established cell line of rat thoracic aorta cells (A10 cells). Underlying mechanisms of agonist-stimulated [Mg2+]i changes were assessed in A10 cells by pharmacologically manipulating phospholipase C, protein kinase C, and the Na+/H+ exchanger. In addition, the dependence of [Mg2+]i on intracellular Ca2+ was determined. [Mg2+]i was measured in single cells by fluorescent digital imaging using mag-fura-2/AM. Basal [Mg2+]i levels in Wistar Kyoto rat and A10 cells were 0.62 +/- 0.02 mmol/liter and 0.58 +/- 0.01 mmol/liter, respectively. Angiotensin II and vasopressin induced a dose-dependent biphasic [Mg2+]i response where [Mg2+]i increased rapidly and transiently to a peak level and then declined to subbasal levels, which were sustained. Preexposure of cells to neomycin, a nonspecific phospholipase C inhibitor, U-73122, a selective phospholipase C inhibitor, calphostin C, a selective protein kinase C inhibitor, and 5-(N, N-hexamethylene)amiloride, a selective Na+/H+ exchange blocker, attenuated angiotensin II- and vasopressin-induced [Mg2+]i responses in a concentration-dependent manner. Removal of extracellular Na+ completely inhibited agonist-elicited [Mg2+]i transients. To determine whether intracellular free Ca2+ concentration ([Ca2+]i) influences agonist-induced [Mg2+]i changes, thapsigargin, a selective sarcoplasmic reticular Ca2+-ATPase inhibitor, was used to deplete intracellular Ca2+ stores. In thapsigargin-pretreated cells, angiotensin II-elicited [Ca2+]i responses were significantly attenuated, whereas agonist-induced [Mg2+]i responses were unchanged. These data demonstrate that in primary cultured VSMC and in an established VSMC line, angiotensin II and vasopressin modulate [Mg2+]i through receptor-mediated pathways, which are [Ca2+]i-independent but which involve phospholipase C, protein kinase C, and the Na+/H+ exchanger. These pathways are linked to a Na+-dependent Mg2+ transporter, which facilitates transmembrane Mg2+ transport.
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PMID:Angiotensin II and vasopressin modulate intracellular free magnesium in vascular smooth muscle cells through Na+-dependent protein kinase C pathways. 879 89

We studied the specific binding of radiolabeled bradykinin ([3H]BK) and vasopressin ([3H]AVP) to membrane preparations of bovine and porcine kidney medulla. [3H]BK reversibly labeled a single site (Kd = 1.06 nM) in bovine kidney medulla independently of [Mg2+]. The number of BK receptors in bovine kidney medulla, Bmax = 122 fmol/mg protein, is markedly (2- to 3-fold) higher than that reported in other tissues. Further characterization by ligand binding indicated that the bovine bradykinin receptor was the B2a subtype, pharmacologically related to B2a receptors expressed by human and rabbit tissues. In contrast, the specific binding of [3H]BK, but not [3H]AVP, to porcine kidney medulla (Kd = 0.32 nM, Bmax = 45 fmol/mg) was dependent upon the presence of enzyme inhibitors to prevent the rapid and selective degradation of bradykinin. Interspecies differences were revealed for renal medulla V2 vasopressin receptors with respect to their abundance and their affinity for several V2-selective ligands. In summary, (i) bovine kidney medulla is a convenient source of tissue for studying the B2a bradykinin receptor subtype; (ii) there are significant species-dependent differences in both the abundance of renal medulla B2a and V2 receptors and the ligand selectivity of V2 receptors; and (iii) these findings are significant in relation to the physiological and pathological roles of renal kinins and their interaction with the neurohypophysial peptide hormone system.
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PMID:Renal bradykinin and vasopressin receptors: ligand selectivity and classification. 884 Feb 90

We recently cloned extracellular Ca(2+)-sensing receptors (CaRs) from bovine parathyroid and rat kidney that play key roles in Ca2+ homeostasis. Inactivating mutations of the CaR in the inherited human disorder, familial hypocalciuric hypercalcemia, cause reduced responsiveness of the parathyroid to extracellular Ca2+ (Cao2+), as well as abnormally avid renal tubular reabsorption of both Ca2+ and Mg2+ in the distal tubule, suggesting an important role for the CaR in regulating parathyroid hormone (PTH) secretion and renal handling of divalent cations. High Cao2+ also inhibits vasopressinstimulated adenosine 3',5'-cyclic monophosphate accumulation in the medullary thick ascending limb (MTAL) and water reabsorption in the collecting duct (CD) and modulates various other aspects of renal function. The relevance of the CaR to these processes, however, is uncertain. Reduced responsiveness of vasopressin-and PTH-mediated actions on the kidney have been described in the newborn that could potentially reflect effects of the CaR on these aspects of renal function. To define further the role of the CaR in regulating renal function, including the above-mentioned changes during the perinatal period, therefore, we have studied its ontogeny in rat kidney. Northern and Western blot analyses, as well as immunohistochemistry with CaR-specific probes, demonstrate that there is little prenatal expression of the extracellular Ca(2+)-sensing receptor, except in large tubules and branching ureteric buds of developing nephrons. Postnatally, CaR mRNA and protein increase markedly during the 1st wk, related principally to expression of the receptor in the developing TAL and, to a lesser extent, in the CD. The level of expression of the receptor remains nearly constant after postnatal day 14. These results demonstrate that the perinatal increases in expression of CaR mRNA and protein parallel its tissue-specific renal expression. Furthermore, it is possible that some of the previously described changes in renal handling of divalent cations and water in the perinatal and immediate postnatal period are related, in part, to the increasing levels of expression of the CaR and resultant inhibitory effects on the actions of PTH and antidiuretic hormone on the developing nephron.
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PMID:Ontogeny of the extracellular calcium-sensing receptor in rat kidney. 885 37

1. The ionic basis of the histamine-induced depolarization of immunohistochemically identified neurones in the supraoptic nucleus (SON) was investigated in the hypothalamo-neurohypophysial explant of male rats. Histamine (0.1-100 microM) caused an H1 receptor-mediated, dose-dependent depolarization of fifty of sixty-two vasopressin neurones in the SON. In contrast, twenty-three oxytocin neurones were either depolarized (n = 6), hyperpolarized (n = 4), or unaffected (n = 13) by histamine. Due to the low percentage of responding cells, oxytocin neurones were not further investigated. 2. Chelation of intracellular Ca2+ with 1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid (BAPTA; 100-500 mM) blocked the depolarization, whereas blocking Ca2+ influx and synaptic transmission with equimolar Co2+ or elevated (5-20 mM) Mg2+ in nominally Ca(2+)-free solutions was without effect. 3. The amplitude of the histamine-induced depolarization was relatively independent of membrane potential. The input resistance was unaltered by histamine in nine neurones, but in nine other neurones it was decreased and in two neurones it was increased by more than 5%. Neither elevating extracellular K+ nor addition of the K+ channel blockers, apamin, d-tubocurarine, tetraethylammonium (TEA), or intracellular Cs+ decreased the histamine effect. Indeed, broadly blocking K+ currents with TEA and Cs+ significantly increased the depolarization to histamine. 4. Tetrodotoxin (2-3 microM) did not inhibit the histamine-induced depolarization. However, equimolar replacement of approximately 50% of extracellular Na+ with Tris+ or N-methyl-D-glucamine reduced or eliminated the response. 5. The depolarization of vasopressin neurones by histamine thus requires extracellular Na+ and intracellular Ca2+. Activation of a Ca(2+)-activated non-specific cation current or a Ca(2+)-Na+ pump are possible mechanisms for this effect.
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PMID:The ionic dependence of the histamine-induced depolarization of vasopressin neurones in the rat supraoptic nucleus. 888 57


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