Membrane potential controls calcium entry into descending vasa recta pericytes

2002 ◽  
Vol 283 (4) ◽  
pp. R949-R957 ◽  
Author(s):  
Zhong Zhang ◽  
Kristie Rhinehart ◽  
Thomas L. Pallone
Keyword(s):  
Membrane Potential ◽  
Channel Blocker ◽  
Calcium Entry ◽  
Ang Ii ◽  
Channel Blockade ◽  
Voltage Gated ◽  
Vasa Recta ◽  
Intracellular Ca ◽  
Bayk 8644

We tested the hypothesis that constriction of descending vasa recta (DVR) is mediated by voltage-gated calcium entry. K+ channel blockade with BaCl2 (1 mM) or TEACl (30 mM) depolarized DVR smooth muscle/pericytes and constricted in vitro-perfused vessels. Pericyte depolarization by 100 mM extracellular KCl constricted DVR and increased pericyte intracellular Ca2+ ([Ca2+]i). The KATP channel opener pinacidil (10−7-10−4 M) hyperpolarized resting pericytes, repolarized pericytes previously depolarized by ANG II (10−8 M), and vasodilated DVR. The DVR vasodilator bradykinin (10−7 M) also reversed ANG II depolarization. The L-type Ca2+ channel blocker diltiazem vasodilated ANG II (10−8 M)- or KCl (100 mM)-preconstricted DVR, and the L-type agonist BayK 8644 constricted DVR. The plateau phase of the pericyte [Ca2+]i response to ANG II was inhibited by diltiazem. These data support the conclusion that DVR vasoreactivity is controlled through variation of membrane potential and voltage-gated Ca2+ entry into the pericyte cytoplasm.

Role of chloride in constriction of descending vasa recta by angiotensin II

2001 ◽  
Vol 280 (6) ◽  
pp. R1878-R1886 ◽  
Author(s):  
Zhong Zhang ◽  
James M. C. Huang ◽  
Malcolm R. Turner ◽  
Kristie L. Rhinehart ◽  
Thomas L. Pallone
Keyword(s):  
Membrane Potential ◽  
Chloride Channels ◽  
Channel Blocker ◽  
Chloride Ion ◽  
Ang Ii ◽  
Vasa Recta ◽  
Gramicidin D ◽  
Chloride Channel Blocker ◽  
Increased Activity

We investigated the dependence of ANG II (10−8 M)-induced constriction of outer medullary descending vasa recta (OMDVR) on membrane potential (Ψm) and chloride ion. ANG II depolarized OMDVR, as measured by fully loading them with the voltage-sensitive dye bis[1,3-dibutylbarbituric acid-(5)] trimethineoxonol [DiBAC4(3)] or selectively loading their pericytes. ANG II was also observed to depolarize pericytes from a resting value of −55.6 ± 2.6 to −26.2 ± 5.4 mV when measured with gramicidin D-perforated patches. When measured with DiBAC4(3) in unstimulated vessels, neither changing extracellular Cl− concentration ([Cl−]) nor exposure to the chloride channel blocker indanyloxyacetic acid 94 (IAA-94; 30 μM) affected Ψm. In contrast, IAA-94 repolarized OMDVR pretreated with ANG II. Neither IAA-94 (30 μM) nor niflumic acid (30 μM, 1 mM) affected the vasoactivity of unstimulated OMDVR, whereas both dilated ANG II-preconstricted vessels. Reduction of extracellular [Cl−] from 150 to 30 meq/l enhanced ANG II-induced constriction. Finally, we identified a Cl−channel in OMDVR pericytes that is activated by ANG II or by excision into extracellular buffer. We conclude that constriction of OMDVR by ANG II involves pericyte depolarization due, in part, to increased activity of chloride channels.

scholarly journals Assessment of Intracellular Calcium and Plasmalemmal Membrane Potential in Cryopreserved Metaphase II Mouse Oocytes

2020 ◽  
Author(s):  
Omar Farhan Ammar ◽  
Therishnee Moodley
Keyword(s):  
Membrane Potential ◽  
Xenopus Oocytes ◽  
Channel Blocker ◽  
Oocyte Activation ◽  
Human Oocytes ◽  
Mouse Oocytes ◽  
Failed Fertilization ◽  
Intracellular Ca ◽  
In Vitro Ageing

Abstract Objectives: Ca2+ is critical for normal oocyte activation and fertilization, and any alteration to the Ca2+ homeostasis may lead to failed fertilization or even cell death. It has been shown that intracellular Ca2+ is increased in bovine and human oocytes when cultured in vitro. Additionally, ATP sensitive potassium channels have been characterised recently in human and Xenopus oocytes. Glibenclamide a KATP channel blocker was shown to protect human oocytes from Ca+2 overloading via inhibition of plasmalemmal KATP channels. This research note aims to demonstrate the effects of oxidative stress and in vitro ageing on the intracellular Ca+2 and plasmalemmal membrane potential dynamics in cryopreserved metaphase II (MII) mouse oocytes. Also, this study aims to show if glibenclamide (a KATP channel blocker ) has a role in regulating intracellular Ca+2 and plasmalemmal membrane potential through KATP channels in cryopreserved metaphase II mouse oocytes.Results: our data did not show an increase in intracellular Ca2+ in untreated cryopreserved mouse oocytes loaded with Fluo-3 AM dye. However, an increase in the plasmalemmal membrane potential was noticed (hyperpolarization). Glibenclamide has shown no significant effect on Ca2+ and plasmalemmal membrane potential.

Ca2+ signaling and membrane potential in descending vasa recta pericytes and endothelia

2002 ◽  
Vol 283 (4) ◽  
pp. F852-F860 ◽  
Author(s):  
Kristie Rhinehart ◽  
Zhong Zhang ◽  
Thomas L. Pallone
Keyword(s):  
Membrane Potential ◽  
Enzymatic Digestion ◽  
Ang Ii ◽  
Cell Type ◽  
Potential Measurement ◽  
Fura 2 ◽  
Vasa Recta ◽  
Cell Recording ◽  
Intracellular Ca ◽  
Inside Out

We devised a method for removal of pericytes from isolated descending vasa recta (DVR). After enzymatic digestion, aspiration of a descending vas rectum into a micropipette strips the pericytes from the abluminal surface. Pericytes and denuded endothelia can be recovered for separate study. Using fura 2-loaded preparations, we demonstrated that 10 nM angiotensin II (ANG II) elevates pericyte intracellular Ca2+ concentration ([Ca2+]i) and suppresses endothelial [Ca2+]i. The anion transport blocker probenecid helps retain fura 2 in the pericyte cytoplasm. DVR endothelia were accessed for membrane potential measurement by perforated-patch whole cell recording by using the pericyte-stripping technique and by turning nondigested vessels inside out with concentric micropipettes. By either method of access, 10 nM ANG II depolarized ( n = 20) and 100 nM bradykinin hyperpolarized ( n = 25) the endothelia. We conclude that isolated endothelia and pericytes remain functional for study of [Ca2+]i responses and that ANG II and bradykinin receptors exist separately on each cell type.

scholarly journals Assessment of Intracellular Calcium and Plasmalemmal Membrane Potential in Cryopreserved Metaphase II Mouse Oocytes

2020 ◽  
Author(s):  
Omar Farhan Ammar ◽  
Therishnee Moodley
Keyword(s):  
Membrane Potential ◽  
Xenopus Oocytes ◽  
Channel Blocker ◽  
Oocyte Activation ◽  
Suitable Alternative ◽  
Human Oocytes ◽  
Mouse Oocytes ◽  
Failed Fertilization ◽  
Intracellular Ca

Abstract Objectives: Ca2+ is critical for normal oocyte activation and fertilization, and any alteration to the Ca2+ homeostasis may lead to failed fertilization or even cell death. It has been shown that intracellular Ca2+ is increased in bovine and human oocytes when cultured in vitro. Additionally, ATP sensitive potassium channels have been characterised recently in human and Xenopus oocytes Glibenclamide a KATP channel blocker was shown to protect human oocytes from Ca+2 overloading. None of these studies have been conducted in mouse oocytes to determine if they are a suitable alternative to human oocytes in the research setting. Thus, this research note aims to demonstrate if cryopreserved metaphase II (MII) mouse oocytes show similar Ca+2 and plasmalemmal membrane potential dynamics to those in human oocytes. Also, to show if glibenclamide influences Ca+2, and plasmalemmal membrane potential in cryopreserved metaphase II mouse oocytes. Results: our data did not show an increase in intracellular Ca2+ in untreated cryopreserved mouse oocytes loaded with Fluo-3 AM dye. However, an increase in the plasmalemmal membrane potential was noticed (hyperpolarization). Glibenclamide has shown no significant effect on Ca+2, mitochondrial and plasmalemmal membrane potential.

Role of iPLA2 and store-operated channels in agonist-induced Ca2+ influx and constriction in cerebral, mesenteric, and carotid arteries

2008 ◽  
Vol 294 (3) ◽  
pp. H1183-H1187 ◽  
Author(s):  
Kristen M. Park ◽  
Mario Trucillo ◽  
Nicolas Serban ◽  
Richard A. Cohen ◽  
Victoria M. Bolotina
Keyword(s):  
Carotid Arteries ◽  
Cerebral Arteries ◽  
Present Evidence ◽  
Voltage Gated ◽  
Functional Inhibition ◽  
Intracellular Ca ◽  
Dependent Pathway ◽  
Secondary Activation

Store-operated channels (SOC) and store-operated Ca2+ entry are known to play a major role in agonist-induced constriction of smooth muscle cells (SMC) in conduit vessels. In microvessels the role of SOC remains uncertain, in as much as voltage-gated L-type Ca2+ (CaL2+) channels are thought to be fully responsible for agonist-induced Ca2+ influx and vasoconstriction. We present evidence that SOC and their activation via a Ca2+-independent phospholipase A2 (iPLA2)-mediated pathway play a crucial role in agonist-induced constriction of cerebral, mesenteric, and carotid arteries. Intracellular Ca2+ in SMC and intraluminal diameter were measured simultaneously in intact pressurized vessels in vitro. We demonstrated that 1) Ca2+ and contractile responses to phenylephrine (PE) in cerebral and carotid arteries were equally abolished by nimodipine (a CaL2+ inhibitor) and 2-aminoethyl diphenylborinate (an inhibitor of SOC), suggesting that SOC and CaL2+ channels may be involved in agonist-induced constriction of cerebral arteries, and 2) functional inhibition of iPLA2β totally inhibited PE-induced Ca2+ influx and constriction in cerebral, mesenteric, and carotid arteries, whereas K+-induced Ca2+ influx and vasoconstriction mediated by CaL2+ channels were not affected. Thus iPLA2-dependent activation of SOC is crucial for agonist-induced Ca2+ influx and vasoconstriction in cerebral, mesenteric, and carotid arteries. We propose that, on PE-induced depletion of Ca2+ stores, nonselective SOC are activated via an iPLA2-dependent pathway and may produce a depolarization of SMC, which could trigger a secondary activation of CaL2+ channels and lead to Ca2+ entry and vasoconstriction.

Vasoconstriction of outer medullary vasa recta by angiotensin II is modulated by prostaglandin E2

1994 ◽  
Vol 266 (6) ◽  
pp. F850-F857 ◽  
Author(s):  
T. L. Pallone
Keyword(s):  
Angiotensin Ii ◽  
Prostaglandin E2 ◽  
Regional Blood Flow ◽  
Renal Medulla ◽  
Hydraulic Pressure ◽  
Vascular Bundles ◽  
Ang Ii ◽  
Vasa Recta ◽  
Anatomical Arrangement

Vasa recta were dissected from outer medullary vascular bundles in the rat and perfused in vitro. Examination by transmission electron microscopy reveals them to be only outer medullary descending vasa recta (OM-DVR). To establish a method for systematic examination of vasoconstriction, OMDVR were perfused at 5 nl/min with collection pressure increased to 5 mmHg. Under these conditions, transmembrane volume flux was found to be near zero, and the transmural hydraulic pressure gradient was found to be < 15 mmHg. Over a concentration range of 10(-12) to 10(-8) M, abluminal application of angiotensin II (ANG II) caused graded focal vasoconstriction of OMDVR that is blocked by saralasin. Luminal application of ANG II over the same concentration range was much less effective. Abluminal application of prostaglandin E2 (PGE2) shifted the vasoconstrictor response of OMDVR to higher ANG II concentrations. PGE2 reversibly dilated OMDVR that had been preconstricted by ANG II. These results demonstrate that OMDVR are vasoactive segments. Their anatomical arrangement suggests that they play a key role in the regulation of total and regional blood flow to the renal medulla.

Control of descending vasa recta pericyte membrane potential by angiotensin II

2002 ◽  
Vol 282 (6) ◽  
pp. F1064-F1074 ◽  
Author(s):  
Thomas L. Pallone ◽  
James M.-C. Huang
Keyword(s):  
Membrane Potential ◽  
Angiotensin Ii ◽  
Reversal Potential ◽  
Niflumic Acid ◽  
Channel Blockers ◽  
Ang Ii ◽  
Vasa Recta ◽  
Cell Recording ◽  
Inward Currents

Using nystatin perforated-patch whole cell recording, we investigated the role of Cl−conductance in the modulation of outer medullary descending vasa recta (OMDVR) pericyte membrane potential (Ψm) by ANG II. ANG II (10−11 to 10−7 M) consistently depolarized OMDVR and induced Ψm oscillations at lower concentrations. The Cl− channel blockers anthracene-9-decarboxylate (1 mM) and niflumic acid (10 μM) hyperpolarized resting pericytes and repolarized ANG II-treated pericytes. In voltage-clamp experiments, ANG II-treated pericytes exhibited slowly activating currents that were nearly eliminated by treatment with niflumic acid (10 μM) or removal of extracellular Ca2+. Those currents reversed at −31 and −10 mV when extracellular Cl− concentration was 152 and 34 mM, respectively. In pericytes held at −70 mV, oscillating inward currents were sometimes observed; the reversal potential also shifted with extracellular Cl− concentration. We conclude that ANG II activates a Ca2+-dependent Cl− conductance in OMDVR pericytes to induce membrane depolarization and Ψm oscillations.

scholarly journals Mural propagation of descending vasa recta responses to mechanical stimulation

2013 ◽  
Vol 305 (3) ◽  
pp. F286-F294 ◽  
Author(s):  
Zhong Zhang ◽  
Kristie Payne ◽  
Chunhua Cao ◽  
Thomas L. Pallone
Keyword(s):  
Membrane Potential ◽  
Patch Clamp ◽  
Mechanical Stimulation ◽  
Channel Blockade ◽  
Patch Clamp Recording ◽  
Automated Method ◽  
Whole Cell Patch Clamp ◽  
Vasa Recta ◽  
Gated Channel ◽  
Phosphoinositide 3 Kinase

To investigate the responses of descending vasa recta (DVR) to deformation of the abluminal surface, we devised an automated method that controls duration and frequency of stimulation by utilizing a stream of buffer from a micropipette. During stimulation at one end of the vessel, fluorescent responses from fluo4 or bis[1,3-dibutylbarbituric acid-(5)] trimethineoxonol [DiBAC4(3)], indicating cytoplasmic calcium ([Ca2+]CYT) or membrane potential, respectively, were recorded from distant cells. Alternately, membrane potential was recorded from DVR pericytes by nystatin whole cell patch-clamp. Mechanical stimulation elicited reversible [Ca2+]CYT responses that increased with frequency. Individual pericyte responses along the vessel were initiated within a fraction of a second of one another. Those responses were inhibited by gap junction blockade with 18 β-glycyrrhetinic acid (100 μM) or phosphoinositide 3 kinase inhibition with 2-morpholin-4-yl-8-phenylchromen-4-one (50 μM). [Ca2+]CYT responses were blocked by removal of extracellular Ca2+ or L-type voltage-gated channel blockade with nifedipine (10 μM). At concentrations selective for the T-type channel blockade, mibefradil (100 nM) was ineffective. During mechanostimulation, pericytes rapidly depolarized, as documented with either DiBAC4(3) fluorescence or patch-clamp recording. Single stimuli yielded depolarizations of 22.5 ± 2.2 mV while repetitive stimuli at 0.1 Hz depolarized pericytes by 44.2 ± 4.0 mV. We conclude that DVR are mechanosensitive and that rapid transmission of signals along the vessel axis requires participation of gap junctions, L-type Ca2+ channels, and pericyte depolarization.

Ouabain modulation of endothelial calcium signaling in descending vasa recta

2006 ◽  
Vol 291 (4) ◽  
pp. F761-F769 ◽  
Author(s):  
János Pittner ◽  
Kristie Rhinehart ◽  
Thomas L. Pallone
Keyword(s):  
Gap Junctions ◽  
Calcium Signaling ◽  
Calcium Concentration ◽  
Cation Channel ◽  
Cytoplasmic Calcium ◽  
Channel Blockade ◽  
Channel Activation ◽  
Voltage Gated ◽  
Vasa Recta ◽  
Peak Phase

Using fura 2-loaded vessels, we tested whether ouabain modulates endothelial cytoplasmic calcium concentration ([Ca2+]CYT) in rat descending vasa recta (DVR). Over a broad range between 10−10 and 10−4 M, ouabain elicited biphasic peak and plateau [Ca2+]CYT elevations. Blockade of voltage-gated Ca2+ entry with nifedipine did not affect the response to ouabain mitigating against a role for myo-endothelial gap junctions. Reduction of extracellular Na+ concentration ([Na+]o) or Na+/Ca2+ exchanger (NCX) inhibition with SEA-0400 (10−6 M) elevated [Ca2+]CYT, supporting a role for NCX in the setting of basal [Ca2+]CYT. SEA-0400 abolished the [Ca2+]CYT response to ouabain implicating NCX as a mediator. The transient peak phase of [Ca2+]CYT elevation that followed either ouabain or reduction of [Na+]o was abolished by 2-aminoethoxydiphenyl borate (5 × 10−5 M). Cation channel blockade with La3+ (10 μM) or SKF-96365 (10 μM) also attenuated the ouabain-induced [Ca2+]CYT response. Ouabain pretreatment increased the [Ca2+]CYT elevation elicited by bradykinin (10−7 M). We conclude that inhibition of ouabain-sensitive Na+-K+-ATPase enhances DVR endothelial Ca2+ store loading and modulates [Ca2+]CYT signaling through mechanisms that involve NCX, Ca2+ release, and cation channel activation.

Evidence that signal transduction for osmoreception is mediated by stretch-activated ion channels in tilapia

2003 ◽  
Vol 284 (5) ◽  
pp. C1290-C1296 ◽  
Author(s):  
A. P. Seale ◽  
N. H. Richman ◽  
T. Hirano ◽  
I. Cooke ◽  
E. G. Grau
Keyword(s):  
Ion Channels ◽  
Channel Blocker ◽  
Oreochromis Mossambicus ◽  
Cell Swelling ◽  
Simultaneous Measurements ◽  
Perfusion Chamber ◽  
Intracellular Ca ◽  
Stretch Activated Ion Channels

Prolactin (PRL) plays a central role in the freshwater osmoregulation of teleost fish, including the tilapia ( Oreochromis mossambicus). Consistent with this action, PRL release from the tilapia pituitary increases as extracellular osmolality is reduced both in vitro and in vivo. Dispersed tilapia PRL cells were incubated in a perfusion chamber that allowed simultaneous measurements of cell volume and PRL release. Intracellular Ca2+ concentrations were measured from fura 2-loaded PRL cells treated in a similar way. Gadolinium (Gd3+), known to block stretch-activated cation channels, inhibited hyposmotically induced PRL release in a dose-related manner without preventing cell swelling. Nifedipine, an L-type Ca2+ channel blocker, did not prevent the increase in PRL release during hyposmotic stimulation. A high, depolarizing concentration of KCl induced a transient and marked increase of intracellular Ca2+ and release of PRL but did not prevent the rise in intracellular Ca2+ and PRL release evoked by exposure to hyposmotic medium. These findings suggest that a decrease in extracellular osmolality stimulates PRL release through the opening of stretch-activated ion channels, which allow extracellular Ca2+ to enter the cell when it swells.

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