ATP stimulates Ca2+ release from a rapidly exchanging pool in cultured rat epididymal cells

1993 ◽  
Vol 264 (6) ◽  
pp. C1388-C1394 ◽  
Author(s):  
A. Y. Leung ◽  
H. L. Tai ◽  
P. Y. Wong
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
The Other ◽  
Free Solution ◽  
Tetraacetic Acid ◽  
Cl Secretion ◽  
Transient Rise ◽  
Extracellular Compartment ◽  
Dose Dependent Fashion ◽  
Dose Dependent

A study was carried out to investigate an ATP-sensitive Ca2+ pool in rat epididymal cells and its role in transepithelial Cl- secretion. In normal buffered solution containing 2.5 mM free Ca2+, ATP triggered single calcium spikes in a dose-dependent fashion. In nominally Ca(2+)-free solution, the peaks of successive Ca2+ spikes diminished after repeated ATP stimulations. Addition of Sr2+ (2.5 mM) to Ca(2+)-free solution after ATP stimulation did not cause changes in fluorescence signals. However, in the presence of Sr2+, ATP gave rise to apparent repetitive Ca2+ spikes of similar magnitudes after repeated stimulations. Increasing the time of exposure in Ca(2+)-free solution containing 50 microM ethylene glycol-bis(beta-amino-ethyl ether)-N,N,N',N'-tetraacetic acid rapidly decreased the intracellular Ca2+ concentration ([Ca2+]i) response to subsequent ATP stimulation. On the other hand, increasing the time of exposure in Sr(2+)-containing solution in Ca(2+)-depleted cells rapidly increased the apparent [Ca2+]i response to subsequent ATP stimulation. These observations suggested the existence of a Ca2+ pool that was rapidly exchanging with the extracellular compartment. Apical application of ATP elicited a transient rise in short-circuit current across the epididymal epithelium in a dose-dependent fashion, and the response was reduced by prior stimulation with thapsigargin. Ca2+ released from a rapidly exchanging ATP-sensitive store might stimulate Cl- secretion in the epididymis, thereby maintaining the electrolyte contents and fluidity of the epididymal microenvironment.

11-Dehydrocorticosterone, a glucocorticoid metabolite, inhibits aldosterone action in toad bladder

1991 ◽  
Vol 261 (5) ◽  
pp. F873-F879 ◽  
Author(s):  
A. S. Brem ◽  
K. L. Matheson ◽  
J. L. Barnes ◽  
D. J. Morris
Keyword(s):  
Sodium Transport ◽  
Cell Layer ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Hydroxysteroid Dehydrogenase ◽  
Toad Bladder ◽  
Compound A ◽  
Dose Dependent Fashion ◽  
Epithelial Cell Layer ◽  
Dose Dependent

The enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) metabolizes glucocorticoid hormones and diminishes their ability to induce sodium transport. In these studies, we determined the location of this enzyme in toad bladder and assessed the biological role for its 11-dehydro end product. Employing a polyclonal antibody directed toward 11 beta-OHSD and immunofluorescence techniques, we located the enzyme in the epithelial cell layer of the toad bladder. Although corticosterone (10(-7) M) can partially suppress aldosterone (10(-7) M)-stimulated short-circuit current (SCC), a clear excess of corticosterone (10(-6) M) did not inhibit the aldosterone-induced induced (10(-8) M) rise in SCC (n = 6). The 11-dehydro product of corticosterone, 11-dehydrocorticosterone (compound A) added to the serosal bath suppressed aldosterone (10(-8) M) peak SCC (360 min) in a dose-dependent fashion reaching 46 +/- 5% of control values at 10(-5) M (n = 6; P less than 0.001). Compound A (10(-5) M) in the mucosal bath also was capable of partially inhibiting the peak aldosterone rise in SCC to 63 +/- 7% of control values with aldosterone at 10(-8) M (n = 6; P less than 0.01) and to 64 +/- 10% of control values with aldosterone at 10(-7) M (n = 9; P less than 0.01). Compound A alone at 10(-5) M did not have any effect on SCC. Isolated toad bladders were not able to transform compound A (at 10(-8) and 10(-5) M) back to corticosterone. Thus the 11-dehydro end product of 11 beta-OHSD (compound A) may play a biologic role by regulating a component of mineralocorticoid-induced sodium transport.

Ca2+ and cAMP activate different K+ conductances in the human intestinal goblet cell line HT29-Cl.16E

1995 ◽  
Vol 268 (6) ◽  
pp. C1503-C1511 ◽  
Author(s):  
D. Merlin ◽  
X. Guo ◽  
C. L. Laboisse ◽  
U. Hopfer
Keyword(s):  
Membrane Potential ◽  
Cell Line ◽  
Amphotericin B ◽  
Short Circuit ◽  
Short Circuit Current ◽  
The Other ◽  
Secreting Cell ◽  
Cl Secretion ◽  
Rate Limiting ◽  
Camp Levels

The mechanism of regulated Cl- secretion was evaluated in the mucin-secreting cell line HT29-Cl.16E by transepithelial electrophysiology and fura 2 measurements of cytosolic Ca2+. Carbachol by itself was a weak secretagogue, but augmented adenosine 3',5'-cyclic monophosphate (cAMP)-mediated secretion more than twofold, consistent with activation of a rate-limiting K+ conductance. To characterize this conductance, monolayers were apically permeabilized with amphotericin B. At least two types of K+ conductances were identified. One type was activated by elevated cytosolic cAMP levels and inhibited by Ba2+ (inhibitor constant 0.3 mM) in the basolateral solution but was not affected by quinidine or elevated cytosolic Ca2+. The other type was activated by carbachol via cytosolic Ca2+ and was partially inhibited by quinidine (60% inhibition by 2.5 mM quinidine) but was not affected by Ba2+ up to 1 mM. Both conductances appear to be involved in active, transepithelial Cl- secretion in intact monolayers but under different conditions because 1) the cAMP-stimulated short-circuit current (Isc) can be partially inhibited by 1 mM Ba2+ (50%) but not quinidine, 2) the Ba2+ inhibition does not affect the carbachol-induced increase in Isc in cells with elevated cAMP levels, and 3) the carbachol-dependent Isc can be inhibited by quinidine. Therefore, the contribution of the cAMP-dependent K+ conductance appears important for maintaining the membrane potential and therewith Cl- secretion when cAMP is the only messenger for secretion signals, whereas the Ca(2+)-dependent K+ conductance is responsible for the carbachol-stimulated increase in Isc.

Mechanisms of electrolyte transport in rat ileum

1980 ◽  
Vol 238 (3) ◽  
pp. G208-G212
Author(s):  
Y. H. Tai ◽  
R. A. Decker
Keyword(s):  
Transport Mechanism ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Ringer Solution ◽  
Electrolyte Transport ◽  
Secretory Process ◽  
Free Solution ◽  
Rat Ileum ◽  
Ussing Chambers ◽  
Cl Secretion

The short-circuit current (Isc), potential difference (PD), tissue conductance (Gt), and Na and Cl fluxes in the short-circuit state across rat ileum were studied in Ussing chambers using a variety of bathing solutions. In Ringer solution, Isc exceeded net Na absorption and net Cl secretion occurred. Addition of 10 mM glucose increased Isc, PD, Gt, and net Na absorption, which accounts for 70% of the increase in Isc. Removal of HCO3 from Ringer solution did not alter any parameters but increased net Cl secretion due to a decrease in mucosal-to-serosal Cl flux. Reduction by 50% of the [Cl] in HCO3-free solution decreased the net Cl secretion to the level in Ringer solution and increased net Na absorption. Removal of Cl decreased Isc to the value of the net Na absorption and decreased the Na influx across the mucosal membrane by 39%. Isc and PD were near zero and net Cl absorption was observed in a Na-free solution. These results are consistent with the transport mechanism that consists of 1) an electrogenic Na absorptive process that accounts for the Isc, 2) a neutral NaCl-coupled secretory process, and 3) a system by which HCO3- secretion exchanges for Cl- absorption.

Ion transport in dog tracheal mucosa: interaction between calcium and prostaglandins

1984 ◽  
Vol 247 (3) ◽  
pp. C182-C187 ◽  
Author(s):  
F. J. Al-Bazzaz ◽  
V. P. Yadava
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Free Solution ◽  
Tetraacetic Acid ◽  
Tracheal Mucosa ◽  
Progressive Decline ◽  
Ussing Chambers ◽  
Tissue Resistance ◽  
36Cl Fluxes ◽  
Mannitol Flux

Prostaglandins E1 and F2 alpha (PGE1 and PGF2 alpha) stimulate short-circuit current (SCC), tissue conductance (G), and net Cl secretion by canine tracheal mucosa. To determine if these actions of prostaglandins require extracellular Ca we tested the effects of PGE1 and PGF2 alpha on tracheal mucosa mounted in Ussing chambers when one side of the preparation was exposed to 0.2 mM ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid in Krebs-Henseleit solution without Ca. Lack of Ca from the mucosal bath was associated with increased G, lowered potential difference (PD), and severalfold increase of 22Na and 36Cl fluxes in both directions. Addition of 1 microM of PGE1 or PGF2 alpha to the Ca-free mucosal bath raised PD by 6 mV and SCC by 15 microA X cm-2 but decreased G by 1.4 mS X cm-2. Unidirectional 22Na and 36Cl fluxes decreased by 32-49% (n = 7, P less than 0.05). These findings suggest that the increase in G, most likely of the paracellular pathway and brought about by the lack of mucosal Ca, was partially reversible by PGE1 and PGF2 alpha. In contrast, when tissues were exposed to Ca-free solution on their submucosal side, PGE1 or PGF2 alpha were not able to reverse the progressive decline in PD and tissue resistance (n = 8). [14C]mannitol flux increased when Ca was absent from the mucosal bath; then addition of 1 microM PGF2 alpha caused a 37% decline in flux (n = 5). In contrast, the increase in the flux of [14C]mannitol found when the submucosal bath lacked calcium was not reversed by 1 microM PGE1.(ABSTRACT TRUNCATED AT 250 WORDS)

Regional effects of autonomic agents on ion transport across excised canine airways

1982 ◽  
Vol 52 (4) ◽  
pp. 893-901 ◽  
Author(s):  
R. C. Boucher ◽  
J. T. Gatzy
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Main Stem ◽  
Adrenergic Agonists ◽  
Adrenergic Agents ◽  
Cl Secretion ◽  
Regional Effects ◽  
Beta Adrenergic Agonists ◽  
Dose Dependent

The effects of cholinergic and adrenergic agonists and antagonists on ion transport and bioelectric properties of excised canine trachea, main-stem bronchi, and subsegmental bronchi were studied. Acetylcholine (ACh) induced in bronchi a dose-dependent reduction in net Na+ absorption, maximal (30%) at 10(-5) M, that reflected a raised Na+ flux from submucosa to mucosa. Because conductance (G) did not change we speculate that the increased flow in the “passive” direction represents the induction of bidirectional Na+ transport. ACh (10(-4) M) increased net Cl- secretion in the trachea and main-stem bronchi and reduced Na+ absorption. ACh effects in all regions were blocked by atropine. In bronchi, alpha- or beta-adrenergic agonists, 10(-5) and 10(-3) M, raised G and unidirectional Cl- fluxes without affecting short-circuit current (Isc) or inducing Cl- secretion. Small reductions in Na+ absorption were noted at 10(-5) M. In contrast, adrenergic agents increased Isc and Cl- secretion in the trachea. We concluded that neurohumoral agonists induce different patterns of effects on ion transport in central compared with more distal airways. Agonists of both classes induced Cl- secretion in the trachea and reduced but did not abolish net NaCl absorption in the bronchi.

Chloride transport of frog gastric fundus: effects of omeprazole

1986 ◽  
Vol 250 (1) ◽  
pp. G118-G126 ◽  
Author(s):  
M. J. Starlinger ◽  
M. J. Hollands ◽  
P. H. Rowe ◽  
J. B. Matthews ◽  
W. Silen
Keyword(s):  
Chloride Transport ◽  
Electrical Response ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Short Circuit Current ◽  
Gastric Fundus ◽  
Open Circuit ◽  
Cl Secretion ◽  
Transient Rise ◽  
Stimulation By Histamine

Omeprazole (10(-4) M) inhibited H+ secretion and increased potential difference (PD), resistance, and short-circuit current (Isc) in chambered bullfrog gastric mucosa, but the electrical changes developed only in tissues previously exposed to histamine. Net chloride transport (JnetCl) did not change after omeprazole under short-circuited conditions, and Isc increased to become equal to JnetCl. Under open-circuit conditions, JnetCl was reduced by 38%, the decrement attributable to the concomitant increase in PD, as evidenced by a linear relationship between JnetCl and PD in omeprazole-treated mucosae clamped to different PD (0-45 mV). The effect of omeprazole on PD and Isc could be blocked by metiamide and was absent in spontaneously resting tissues. HEPES nutrient solutions did not alter the electrical response or Cl- transport after omeprazole. In Na+-free solutions, omeprazole induced only a transient rise in PD and Isc. We conclude that omeprazole uncouples H+ and Cl- secretion. This Cl- secretion is electrogenic and dependent upon stimulation by histamine. Both Na+ and HCO3- seem to be involved in movement of Cl- across the basolateral membrane.

Endothelin stimulates chloride secretion across canine tracheal epithelium

1991 ◽  
Vol 261 (2) ◽  
pp. L188-L194 ◽  
Author(s):  
P. I. Plews ◽  
Z. A. Abdel-Malek ◽  
C. A. Doupnik ◽  
G. D. Leikauf
Keyword(s):  
Epithelial Cells ◽  
Short Circuit ◽  
Second Messengers ◽  
Short Circuit Current ◽  
Chloride Secretion ◽  
Tracheal Epithelium ◽  
Membrane Phospholipids ◽  
Cl Secretion ◽  
Tracheal Epithelial Cells ◽  
Tracheal Epithelial

The endothelins (ET) are a group of isopeptides produced by a number of cells, including canine tracheal epithelial cells. Because these compounds are endogenous peptides that may activate eicosanoid metabolism, we investigated the effects of ET on Cl secretion in canine tracheal epithelium. Endothelin 1 (ET-1) was found to produce a dose-dependent change in short-circuit current (Isc) that increased slowly and reached a maximal value within 10-15 min. When isopeptides of ET were compared, 300 nM ET-1 and ET-2 produced comparable maximal increases in Isc, whereas ET-3 produced smaller changes in Isc (half-maximal concentrations of 2.2, 7.2, and 10.4 nM, respectively). Ionic substitution of Cl with nontransported anions, iodide and gluconate, reduced ET-1-induced changes in Isc. Furthermore, the response was inhibited by the NaCl cotransport inhibitor, furosemide. In paired tissues, ET-1 significantly increased mucosal net 36Cl flux without significant effect on 22Na flux. The increase in Isc induced by ET was diminished by pretreatment with indomethacin. The second messengers mediating the increase in Isc were investigated in cultured canine tracheal epithelial cells. ET-1 stimulated the release of [3H]arachidonate from membrane phospholipids, increased intracellular Ca2+ (occasionally producing oscillations), and increased adenosine 3',5'-cyclic monophosphate accumulation. The latter was diminished by indomethacin. Thus ET is a potent agonist of Cl secretion (with the isopeptides having the following potency: ET-1 greater than or equal to ET-2 greater than ET-3) and acts, in part, through a cyclooxygenase-dependent mechanism.

scholarly journals Zinc inhibits cAMP-stimulated Cl secretion via basolateral K-channel blockade in rat ileum

2005 ◽  
Vol 288 (5) ◽  
pp. G956-G963 ◽  
Author(s):  
Kazi Mirajul Hoque ◽  
Vazhaikkurichi M. Rajendran ◽  
Henry J. Binder
Keyword(s):  
Short Circuit ◽  
Basolateral Membrane ◽  
Short Circuit Current ◽  
K Channel ◽  
Isolated Cells ◽  
Rat Ileum ◽  
Anion Secretion ◽  
Cl Secretion ◽  
Ion Absorption ◽  
Isotonic Buffer

Zn, an essential micronutrient and second most abundant trace element in cell and tissues, reduces stool output when administered to children with acute diarrhea. The mechanism by which Zn improves diarrhea is not known but could result from stimulating Na absorption and/or inhibiting anion secretion. The aim of this study was to investigate the direct effect of Zn on intestinal epithelial ion absorption and secretion. Rat ileum was partially stripped of serosal and muscle layers, and the mucosa was mounted in lucite chambers. Potential difference and short-circuit current were measured by conventional current-voltage clamp method.86Rb efflux and uptake were assessed for serosal K channel and Na-K-2Cl cotransport activity, respectively. Efflux experiments were performed in isolated cells preloaded with86Rb in the presence of ouabain and bumetanide, whereas uptake experiments were performed in low-Cl isotonic buffer containing Ba and ouabain. Neither mucosal nor serosal Zn affected glucose-stimulated Na absorption. In contrast, forskolin-induced Cl secretion was markedly reduced by serosal but not mucosal addition of Zn. Zn also substantially reversed the increase in Cl secretion induced by 8-bromoadenosine 3′,5′-cyclic monophosphate (8-BrcAMP) with half-maximal inhibitory concentration of 0.43 mM. In contrast, serosal Zn did not alter Cl secretion stimulated by carbachol, a Ca-dependent agonist. Zn inhibited 8-BrcAMP-stimulated86Rb efflux but not carbachol-stimulated86Rb efflux. Zn had no effect on bumetanide-sensitive86Rb uptake, Na-K-ATPase, or CFTR. We conclude from these studies that Zn inhibits cAMP-induced Cl secretion by blocking basolateral membrane K channels.

Mechanisms of sodium and chloride transport across equine tracheal epithelium

1990 ◽  
Vol 259 (6) ◽  
pp. L459-L467 ◽  
Author(s):  
G. J. Tessier ◽  
T. R. Traynor ◽  
M. S. Kannan ◽  
S. M. O3'Grady
Keyword(s):  
Chloride Transport ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Short Circuit Current ◽  
Ringer Solution ◽  
Tracheal Epithelium ◽  
Ussing Chambers ◽  
Cl Secretion ◽  
Cotransport System ◽  
Ethanesulfonic Acid

Equine tracheal epithelium, stripped of serosal muscle, mounted in Ussing chambers, and bathed in plasmalike Ringer solution generates a serosa-positive transepithelial potential of 10–22 mV and a short-circuit current (Isc) of 70–200 microA/cm2. Mucosal amiloride (10 microM) causes a 40–60% decrease in Isc and inhibits the net transepithelial Na flux by 95%. Substitution of Cl with gluconate resulted in a 30% decrease in basal Isc. Bicarbonate substitution with 20 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid decreased the Isc by 21%. The Cl-dependent Isc was inhibited by serosal addition of 1 mM amiloride. Bicarbonate replacement or serosal amiloride (1 mM) inhibits the net Cl flux by 72 and 69%, respectively. Bicarbonate replacement significantly reduces the effects of serosal amiloride (1 mM) on Isc, indicating its effect is HCO3 dependent. Addition of 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP; 100 microM) causes a 40% increase in Isc. This effect is inhibited by subsequent addition of 10 microM serosal bumetanide. Bumetanide (10 microM) reduces net Cl secretion following stimulation with 8-BrcAMP (100 microM). Serosal addition of BaCl2 (1 mM) causes a reduction in Isc equal to that following Cl replacement in the presence or absence of 100 microM cAMP. These results suggest that 1) Na absorption depends on amiloride-inhibitable Na channels in the apical membrane, 2) Cl influx across the basolateral membrane occurs by both a Na-H/Cl-HCO3 parallel exchange mechanism under basal conditions and by a bumetanide-sensitive Na-(K?)-Cl cotransport system under cAMP-stimulated conditions, and 3) basal and cAMP-stimulated Cl secretion depends on Ba-sensitive K channels in the basolateral membrane.

Use of a modified Ussing chamber to monitor intestinal epithelial and smooth muscle functions

1991 ◽  
Vol 261 (1) ◽  
pp. G166-G170 ◽  
Author(s):  
Y. F. Li ◽  
N. W. Weisbrodt ◽  
Y. Harari ◽  
F. G. Moody
Keyword(s):  
Smooth Muscle ◽  
Strain Gauge ◽  
Short Circuit ◽  
Ussing Chamber ◽  
Short Circuit Current ◽  
Displacement Transducer ◽  
Organ Bath ◽  
Force Displacement ◽  
Dose Dependent ◽  
Muscle Functions

A technique that allows the simultaneous monitoring of epithelial and smooth muscle function was developed and used to study rat small intestine in vitro. A Ussing chamber was modified so that a strain gauge force transducer could be sewn to the serosal surface of an intestinal segment clamped in the chamber. The apparatus was used to monitor short-circuit current, potential difference, and resistance across the segment, and contractions of the longitudinal layer of the muscularis externa. Both spontaneous activity and responses to the application of carbachol were recorded. Carbachol applied to the serosal side induced dose-dependent increases in both short-circuit current and contractile force. The median effective doses of the two responses differed, with contractions being more sensitive to the drug. Carbachol applied to the mucosal side induced no changes in either epithelial or contractile activities. The ability of the serosal strain gauge transducer to monitor contractions faithfully was tested in an organ bath in which the gut segment was attached to an external force-displacement transducer. There was a close correlation between the dose-dependent increase in force in response to carbachol measured by the serosal transducer and that measured by the force-displacement transducer (r = 0.988). Thus our technique can be used to study simultaneously epithelial and smooth muscle functions of the intestine.

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