Calcium-Dependent K-Channels in Guinea Pig and Human Urinary Bladder

Trivedi, Shephali; Potter-Lee, L.; Li, J H; Yasay, G.D.; Russell, Keith; Ohnmacht, Cyrus J.; Empfield, James R.; Trainor, Diane A.; Kau, Sen T.

doi:10.1006/bbrc.1995.2146

Cited by 29 publications

(15 citation statements)

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“…IbTX is a specific and powerful inhibitor of large-conductance K Ca channels [7], suggesting the involvement of this class of channel in the K + efflux increase observed during an ATP challenge. We clearly show that NS004, a BK Ca opener [14,37], induces a rise in K + efflux, confirming the presence of large-conductance K Ca channels in neurohypophysial glial cells.…”

Section: Discussionsupporting

confidence: 61%

Potassium efflux triggered by P2Y purinoceptor activation in cultured pituicytes

Troadec

Thirion

Petturiti

et al. 2000

Pflugers Arch - Eur J Physiol

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We have previously investigated the effects of extracellular ATP on the concentration of free cytosolic calcium ([Ca2+]i) from rat cultured neurohypophysial astrocytes (pituicytes). We demonstrated that ATP acts via a P2Y receptor to increase [Ca2+]i. In the present study, we examine the effect of ATP on K+ efflux using 86Rb+ as an isotopic tracer, in order to characterize the possible presence of a Ca2+-activated K+ conductance and to establish the implications of pituicytes in the regulation of stimulus-secretion coupling. ATP evoked an increase in 86Rb+ efflux from cultured pituicytes. This effect was Ca2+ dependent, as indicated by the unresponsiveness of cells loaded with BAPTA/AM (20 microM). Furthermore, the effect of ATP was mimicked by 2-methylthio-adenosine-5'-triphosphate (2MeSATP), a P2 purinoceptor agonist, and abolished by Reactive Blue 2 (RB-2), a selective P2Y antagonist, implying a role for the P2Y purinoreceptor. A pharmacological study revealed that Ba2+ and tetraethylammonium (TEA), two inhibitors of K+ channels, both strongly reduced the ATP-stimulated 86Rb+ efflux. In addition, the effect of ATP was modulated by different peptidic toxins. Apamin (100 nM), an inhibitor of the small-conductance Ca2+-activated K+ channels, partly blocked ATP-induced 86Rb+ efflux. Leiurus quinquestriatus hebraeus (LQH) scorpion venom (20 microg/ml) and Buthus tamulus (BT) scorpion venom (20-200 microg/ml) inhibited ATP-induced 86Rb+ efflux. The specificity of the effects of the crude venoms was checked using charybdotoxin (100 nM) and iberiotoxin (1 pM), which are the active toxins extracted from the LQH and BT venoms, respectively. These data indicate the involvement of several types of Ca2+-activated K+ channels in the ATP-dependent K+ efflux, and lead to the proposal that, in the neurohypophysis, extracellular ATP released by nerve terminals may act directly on the pituicytes and induce a K+ efflux via a P2Y purinoreceptor.

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Section: Discussionsupporting

confidence: 61%

Potassium efflux triggered by P2Y purinoceptor activation in cultured pituicytes

Troadec

Thirion

Petturiti

et al. 2000

Pflugers Arch - Eur J Physiol

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“…In detrusor two of these channels have received particular attention, the intracellular CaZ+-activated K + channel, K(Ca) channel, and the ATP-sensitive K + channel, K(ATP) channel K(Ca) channels exist as either a large (BK) or small (SK) channel conductance subtypes, and are blocked selectively by charybdotoxin (or iberiotoxin) and apamin, respectively. The BK channel subtype is considered the more important in both animal and human detrusor, by contributing a significant role to repolarization of the action potential and the maintainence of the resting potential [21,22]. Changes to the intracellular Ca 2+ in the physiological range (10 nM to about 1 /~M), generated either artificially or by modulators of intraceltular Ca 2+ regulation, altered channel conductance [23,24].…”

Section: K § Channels In Detrusor Smooth Musclementioning

confidence: 99%

Electrophysiological properties of the bladder

Fry

Sui

1998

Int Urogynecol J

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The electrophysiological properties of detrusor smooth muscle are described, in particular with regard to their influence on the contractile properties of the tissue. The Ca2+ and K+ channel activities are most important in generating action potentials, but the role of several other ionic currents is described, including Cl-, Ca2+-activated, stretch-activated and ligand-gated channels. The variable appearance and functions of different ionic currents in disease states is discussed, as well as the question of whether electrical activity can transmit between adjacent smooth muscle cells. In addition, the precise role that electrophysiological phenomena play in the regulation of the contractile state of the smooth muscle cells, as well as the generation of bladder electromyograms, is discussed.

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“…The list of these potassium channels includes K ATP (Bonev and Nelson, 1993;Trivedi et al, 1994;Gopalakrishnan et al, 1999), maxi-K ϩ (Trivedi et al, 1995;Herrera et al, 2000;Siemer et al, 2000), SK family (Herrera et al, 2000(Herrera et al, , 2003Ohya et al, 2000), members of the voltage-gated K v family (Davies et al, 2002;Thorneloe and Nelson, 2003), and, possibly, members of the KCNQ family of potassium channels (Argentieri and Sheldon, 2001). Opening of potassium channels leads to an increase in potassium efflux from the cell and produces a hyperpolarization of the membrane potential, thereby decreasing the activation of voltage-dependent calcium channels.…”

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confidence: 99%

BL-1249 [(5,6,7,8-Tetrahydro-naphthalen-1-yl)-[2-(1H-tetrazol-5-yl)-phenyl]-amine]: A Putative Potassium Channel Opener with Bladder-Relaxant Properties

Tertyshnikova

Knox²,

Plym³

et al. 2004

J Pharmacol Exp Ther

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BL-1249 [(5,6,7,8-tetrahydro-naphthalen-1-yl)-[2-(1H-tetrazol-5-yl)-phenyl]-amine] produced a concentration-dependent membrane hyperpolarization of cultured human bladder myocytes, assessed as either a reduction in fluorescence of the voltage-sensitive dye bis-(1,2-dibutylbarbituric acid)trimethine oxonol (EC 50 ϭ 1.26 Ϯ 0.6 M) or by direct electrophysiological measurement (EC 50 ϭ 1.49 Ϯ 0.08 M). BL-1249 also produced a membrane hyperpolarization of acutely dissociated rat bladder myocytes. Voltage-clamp studies in human bladder cells revealed that BL-1249 activated an instantaneous, noninactivating current that reversed near E K . The BL-1249-evoked outward K ϩ current was insensitive to blockade by glyburide, tetraethylammonium, iberiotoxin, 4-aminopyridine, apamin, or Mg 2ϩ . However, the current was inhibited by extracellular Ba 2ϩ

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Calcium-Dependent K-Channels in Guinea Pig and Human Urinary Bladder

Cited by 29 publications

References 0 publications

Potassium efflux triggered by P2Y purinoceptor activation in cultured pituicytes

Potassium efflux triggered by P2Y purinoceptor activation in cultured pituicytes

Electrophysiological properties of the bladder

BL-1249 [(5,6,7,8-Tetrahydro-naphthalen-1-yl)-[2-(1H-tetrazol-5-yl)-phenyl]-amine]: A Putative Potassium Channel Opener with Bladder-Relaxant Properties

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