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

Endothelins modulate not only vasoregulation but also neurotransmission and hormone secretion, specifically vasopressin (AVP) secretion. The present studies were designed to ascertain the site of action and the participation of membrane cation channels mediating endothelin-3-induced AVP release. Experiments were performed using standard and compartmentalized hypothalamo-neurohypophysial explants. The stimulatory action of endothelin-3 on AVP release occurred at the neural lobe, consistent with the failure of sodium channel blockade to decrease AVP secretion. Calcium channel antagonism or chelation of extracellular calcium inhibited neurohormone release, but blockade of calcium mobilization from intracellular stores with 8-(diethyl-amino)octyl 3,4,5-trimethoxybenzoate hydrochloride (TMB-8) did not. Inhibition of the calcium-activated potassium channel with charybdotoxin increased AVP levels dose dependently. Potassium ionophore abolished this response, as did TMB-8, but inhibition of calcium entry failed to do so. A subthreshold dose of charybdotoxin potentiated AVP secretion to submaximal stimulation with endothelin-3 that was prevented only by concomitant blockade of calcium influx and intracellular mobilization. The data support interaction between calcium and potassium channels at the secretory terminal. Collectively, these data are consistent with endothelin-3 receptor activation at the secretory terminal initiating calcium entry, thereby leading to depolarization independent of sodium conductances. This mechanism is opposed by hyperpolarizing forces linked to calcium accumulation, namely, the charybdotoxin-sensitive calcium-activate potassium channel. Interaction of the depolarizing and repolarizing systems enables grade AVP secretion from the neural lobe. These findings do not preclude the participation of other systems as well.
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PMID:Cation channel mechanisms in ET-3-induced vasopressin secretion by rat hypothalamo-neurohypophysial explants. 753 90

The endoplasmic reticulum is generally absent from schematic representations of transport phenomena, although it shows a well-organized network in most transport epithelial cells. In order to examine the correlation between this organelle and cellular activity, bladders of Bufo marinus were studied under different experimental conditions and fixed by immersion in glutaraldehyde, followed by OsO4 impregnation for 3 days. Normal granular and mitochondria-rich cells showed a rich cytoplasmic network of canaliculi, well-impregnated by osmium deposits. Following a 2 to 15-min stimulation (serosal bath) with arginine vasopressin, the V2 receptor agonist dD-arginine-vasopressin or cyclic AMP (cAMP), the staining of endoplasmic reticulum in granular cells disappeared. After washing out of the hormone or the agonist, impregnation of the endoplasmic reticulum could be observed once again. Arginine vasopressin did not modify the impregnation of endoplasmic reticulum of either mitochondria-rich or basal cells. Our data indicate a correlation between the reactivity of endoplasmic reticulum to osmium, and a cAMP-dependent effect of arginine vasopressin through its V2 receptors. Incubation of arginine vasopressin through its V2 receptors. Incubation of toad bladders carried out with agents interfering with cellular calcium (calcium ionophores, high or low bath calcium) or with calcium release from the endoplasmic reticulum (TMB-8, thapsigargin) suggested that an early step in the cAMP-dependent effect of arginine vasopressin must involve the release of intracellular calcium from the endoplasmic reticulum. However, calcium ATPases in this organelle do not seem to participate in the hormonal effect.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Reversible histochemical modifications of endoplasmic reticulum following arginine vasopressin stimulation of granular cells of toad bladder. 778 Oct 34

The effects of neuropeptide Y (NPY) on LHRH release from an immortalized cell line were investigated using a flow-through cell culture superfusion system. Immortalized hypothalamic GT1-7 cells were cultured for 72 h and superfused for a total of 180 min. In initial experiments, discrete 5-min pulses of NPY (10(-12)-10(-5) M) were administered to the cells. A clear dose-dependent stimulatory effect on NPY on LHRH release from the cells was observed with a calculated 50% effectiveness concentration of 33 nM. The stimulatory effects of brief NPY exposure were rapid and robust, e.g. reaching and maintaining levels of 173% over baseline for 20 min at the 10(-7) dose. The lowest dose of NPY that showed a significant effect was 10(-10) M; maximal responses were observed at 10(-6) M and reached a plateau thereafter. Control pulses of Dulbecco's modified Eagle's medium (DMEM) and 10(-6) M substance P or arg-vasopressin were also presented to the cells to serve as controls for our pulse protocol, and these challenges produced no significant LHRH responses. The NPY receptor antagonists, PYX1 and PYX2, at 10(-8) M, completely blocked the observed NPY responses in these cells. To assess the NPY receptor subtypes that mediate the NPY effects pharmacologically, GT1-7 cells were challenged with a Y1 receptor agonist, (Leu31Pro34)NPY, a Y2 receptor agonist, NPY(13-36), or peptide YY, at doses 10(-12)-10(-5) M. All four peptides stimulated LHRH release from GT1-7 cells with a rank-ordered potency of NPY = peptide YY > Y1 agonist = Y2 agonist. To examine possible signal transduction mechanism(s) involved in mediating this effect, pertussis toxin, RpcAMPs (cyclic adenosine-3'5'-monophosphothioate Rp diastereomer), Ca(2+)-free DMEM and TMB-8 (3, 4, 5-trimethoxybenzoic acid 8-(diethylamino) octylester) were used to treat the cells before and during superfusion with NPY. Treatment with pertussis toxin, RpcAMPs, and Ca(2+)-free DMEM did not significantly alter NPY-stimulated LHRH release responses to 10(-7) M NPY. However, the addition of 100 microM and 250 microM TMB-8 to Ca(2+)-free DMEM almost completely blocked this NPY effect, as did 10 microM ryanodine. Finally, the locus of action for this NPY effect was examined using tetrodotoxin to reduce action potential propagation in the GT1-7 cells. Tetrodotoxin treatment blocked the LHRH response to NPY by more than 50%.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Neuropeptide Y stimulates luteinizing hormone-releasing hormone release from superfused hypothalamic GT1-7 cells. 792 25

Cellular calcium modulates enzyme activity, cell proliferation, and differentiation. In vascular smooth muscle cells (VSMC), calcium may contribute to increased vascular contractility and structural alterations in both hypertension and atherosclerosis. We investigated the role of calcium in angiotensin II (AII)-induced prostaglandin release and DNA synthesis in VSMC. Prostaglandin levels were determined by radioimmunoassay, and DNA synthesis was determined by the incorporation of [3H]thymidine. AII dose-dependently stimulated the release of prostaglandin E2 and prostaglandin I2, and this effect was synergistically enhanced by the Ca2+ ionophore A23187. Conversely, the AII response was inhibited by EGTA, a chelator of Ca2+ ions and by verapamil and nifedipine, two Ca2+ channel blockers or by incubation of the cells without exogenous Ca2+. TMB-8, an inhibitor of calcium mobilization, also strongly reduced angiotensin response. Similar results were obtained for angiotensin III (AIII) and vasopressin, two other agonists of prostaglandin production. AII- or serum-stimulated DNA synthesis was almost abolished by EGTA, whereas TMB-8, verapamil, and nifedipine had little or no effect. The production of prostaglandins triggered by angiotensins and vasopressin in VSMC is dependent on both intracellular and extracellular calcium, with calcium entering through L-type Ca2+ channels. Extracellular calcium is important for AII and serum mitogenic activity, but L-type Ca2+ channels do not appear to be implicated.
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PMID:Role of calcium in angiotensin II-induced prostaglandin release and DNA synthesis in rat vascular smooth muscle cells. 872 Apr 17

In order to explore the mechanism of action of vanadyl sulfate (VOSO4), previously described as an antidiabetic and antihypertensive agent, we have investigated the role of calcium and tyrosine phosphorylation in the contractile responses of rat aorta or skinned rabbit mesenteric artery rings. VOSO4 induced a concentration-dependent contraction of aorta (pD2 = 3.2), which was potentiated by endothelium removal (pD2 = 4.2). After a first exposure to VOSO4, no change in responsiveness was observed even though high vanadium concentrations had accumulated in the aortic tissue (approximately 4 x 10(-3) M). VOSO4 induced, in calcium-free medium, a significant response that, relative to contractions measured in Krebs-Henseleit buffer, was higher (36%) than norepinephrine (16%)-, arginine-vasopressin (8%)- or KCI (5%)-induced responses. 8-(N,N-diethylamino)octyl 3,4,5-trimethoxybenzoate hydrochloride (TMB-8), an intracellular calcium release inhibitor, did not modify VOSO4-induced response either in the presence or in the absence of ambient calcium. On skinned preparations, VOSO4 antagonized Ca++-induced contraction. The tyrosine kinase inhibitors tyrphostin 23 (T23) and tyrphostin 47 (T47) potentiated by 4- and 14-fold, respectively, the activity of VOSO4, in contrast to the lack of effect of T47 on pervanadate-induced contraction. When phosphotyrosine content was revealed by Western blotting, VOSO4 had no effect alone, but in the presence of T47, it dramatically increased the phosphotyrosine content. This result contrasts again with PV-induced tyrosine phosphorylation, which was blocked by T47. These data suggest that the signaling events involved in vascular effects of VOSO4, although they depend little on calcium mobilization, are related to tyrosine phosphorylation, likewise through a pathway different from that of pervanadate.
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PMID:Characterization of vanadyl sulfate effect on vascular contraction: roles of calcium and tyrosine phosphorylation. 910 36

In the present study, we examined the effect of vasopressin on the induction of the low-molecular-weight heat shock proteins heat shock protein 27 (HSP27) and alphaB-crystallin in an aortic smooth muscle cell line, A10 cells. Vasopressin induced a time-dependent accumulation of HSP27 and alphaB-crystallin. The stimulatory effects of vasopressin were dose-dependent over the range 0.1 nmol/L to 0.1 micromol/L. The EC50 values for vasopressin were 2 (HSP27) and 4 nmol/L (alphaB-crystallin). Vasopressin induced increases in the levels of the mRNAs for HSP27 and alphaB-crystallin. 12-O-Tetradecanoylphorbol 13-acetate (TPA), a protein kinase C (PKC)-activating phorbol ester, induced an accumulation of HSP27 (EC50, 20 nmol/L) and alphaB-crystallin (EC50, 2 nmol/L). In contrast, 4alpha-phorbol 12,13-didecanoate, a non-PKC-activating phorbol ester, had no such effect. Staurosporine and calphostin C, inhibitors of PKC, significantly reduced the vasopressin-induced accumulation of HSP27 and alphaB-crystallin as well as that induced by TPA. BAPTA/AM and TMB-8, inhibitors of intracellular Ca2+ mobilization, significantly reduced the vasopressin-induced accumulation of HSP27 and alphaB-crystallin. These results strongly suggest that vasopressin stimulates the induction of HSP27 and alphaB-crystallin via PKC activation in vascular smooth muscle cells and that this effect of vasopressin is dependent on intracellular Ca2+ mobilization.
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PMID:Vasopressin stimulates the induction of heat shock protein 27 and alphaB-crystallin via protein kinase C activation in vascular smooth muscle cells. 992 48

Endogenous ouabain-like factors (OLF) may play a role in the pathogenesis of volume-dependent hypertension by raising intracellular free calcium ([Ca2+]i) as a consequence of inhibition of the sodium pump. In previous studies we described the presence of two low molecular (Mr approximately equals 400) inhibitors of Na-K-ATPase in human urine, ie, a more polar OLF-1 and a more apolar OLF-2. We subsequently identified the active compound in OLF-2 as vanadium (V(IV))-diascorbate (Mr 416). OLF-1, OLF-2, and V-diascorbate inhibited dose-dependently porcine Na-K-ATPase in vitro. In the present study we investigated the effects of urinary OLF-1, OLF-2, and V-diascorbate on calcium mobilization, ie, on [Ca2+]i in cultured rat vascular smooth muscle (VSM) cells in comparison to the effects of ouabain, angiotensin II (A II), and arginine-vasopressin (AVP). [Ca2+]i was determined by the fura-2 method. OLF-1 and OLF-2 (each approximately equals 10(-4) mol/L), obtained as single spots by thin-layer chromatography, produced a rise in [Ca2+]i in VSM cells from 45 +/- 7 to 99 +/- 22 and from 48 +/- 9 to 92 +/- 2 nmol/L (each n = 5; P < .05), respectively, after 3 min. V-diascorbate also increased [Ca2+]i slowly and dose-dependently, eg, from 56 +/- 14 to 102 +/- 15 nmol/L at a concentration of 10(-6) mol/L (n = 5; P < .05) after 3 min. A similar slow rise in [Ca2+]i from 53 +/- 10 to 185 +/- 3 nM (n = 5; P < .05) after 3 min was found with ouabain (10(-6) mol/L). As standard vasoconstrictor, All (10(-8) mol/L) rapidly increased [Ca2+]i from 23 +/- 4 to 846 +/- 50 nmol/L (n = 7; P < .01) within 30 sec. This effect was enhanced to 1,389 +/- 161 nM (n = 7; P < .01) when VSM cells were preincubated with V-diascorbate (10(-6) mol/L) for 10 min. AVP (10(-7) mol/L) also rapidly increased [Ca2+]i to 418 +/-11 nmol/L within 30 sec (n = 7; P < .01). This effect was enhanced in the presence of OLF-2 (approximately equals 10(-4) mol/L) or ouabain (10(-6) mol/L) to 523 +/- 14 and 560 +/- 19 nmol/L, respectively (each n = 7); P < .01). The calcium channel blocker verapamil, the intracellular calcium release blocker TMB-8, and the unselective cation channel blocker Ni2+ partly blunted the A II- or AVP-induced rise in [Ca2+]i and prevented the OLF-2- and V-diascorbate-induced increase in [Ca2+]i. Thus, OLF-1, OLF-2 and V-diascorbate, the active component of OLF-2, reveal effects similar to those of ouabain on [Ca2+]i in VSM cells, ie, they produce a slow rise in [Ca2+]i subsequent to inhibition of the sodium pump. The physiologic and pathologic roles of these and additional OLF in body fluid and blood pressure regulation and in hypertension have yet to be evaluated.
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PMID:Inhibitors of Na-K-ATPase in human urine: effects of ouabain-like factors and of vanadium-diascorbate on calcium mobilization in rat vascular smooth muscle cells: comparison with the effects of ouabain, angiotensin II, and arginine-vasopressin. 1082 37


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