Basolateral Cl− uptake mechanisms in Xenopus laevis lung epithelium

2010 ◽  
Vol 299 (1) ◽  
pp. R92-R100 ◽  
Author(s):  
Jens Berger ◽  
Martin Hardt ◽  
Wolfgang G. Clauss ◽  
Martin Fronius
Keyword(s):  
Xenopus Laevis ◽  
Ion Transport ◽  
Anion Exchanger ◽  
Short Circuit ◽  
Ussing Chamber ◽  
Short Circuit Current ◽  
Transport Processes ◽  
Lung Epithelium ◽  
Active Ion Transport ◽  
Uptake Mechanisms

A thin liquid layer covers the lungs of air-breathing vertebrates. Active ion transport processes via the pulmonary epithelial cells regulate the maintenance of this layer. This study focuses on basolateral Cl− uptake mechanisms in native lungs of Xenopus laevis and the involvement of the Na+/K+/2 Cl− cotransporter (NKCC) and HCO3−/Cl− anion exchanger (AE), in particular. Western blot analysis and immunofluorescence staining revealed the expression of the NKCC protein in the Xenopus lung. Ussing chamber experiments demonstrated that the NKCC inhibitors (bumetanide and furosemide) were ineffective at blocking the cotransporter under basal conditions, as well as under pharmacologically stimulated Cl−-secreting conditions (forskolin and chlorzoxazone application). However, functional evidence for the NKCC was detected by generating a transepithelial Cl− gradient. Further, we were interested in the involvement of the HCO3−/Cl− anion exchanger to transepithelial ion transport processes. Basolateral application of DIDS, an inhibitor of the AE, resulted in a significantly decreased the short-circuit current (ISC). The effect of DIDS was diminished by acetazolamide and reduced by increased external HCO3− concentrations. Cl− secretion induced by forskolin was decreased by DIDS, but this effect was abolished in the presence of HCO3−. These experiments indicate that the AE at least partially contributes to Cl− secretion. Taken together, our data show that in Xenopus lung epithelia, the AE, rather than the NKCC, is involved in basolateral Cl− uptake, which contrasts with the common model for Cl− secretion in pulmonary epithelia.

scholarly journals Enterohemorrhagic E. coli (EHEC)—Secreted Serine Protease EspP Stimulates Electrogenic Ion Transport in Human Colonoid Monolayers

Toxins ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 351 ◽  
Author(s):  
C. Tse ◽  
Julie In ◽  
Jianyi Yin ◽  
Mark Donowitz ◽  
Michele Doucet ◽  
...  
Keyword(s):  
Ion Transport ◽  
Serine Protease ◽  
Shiga Toxin ◽  
Short Circuit ◽  
Ussing Chamber ◽  
Adult Stem Cell ◽  
Short Circuit Current ◽  
Watery Diarrhea ◽  
E Coli ◽  
Electrogenic Ion Transport

One of the characteristic manifestations of Shiga-toxin-producing Escherichia coli (E. coli) infection in humans, including EHEC and Enteroaggregative E. coli O104:H4, is watery diarrhea. However, neither Shiga toxin nor numerous components of the type-3 secretion system have been found to independently elicit fluid secretion. We used the adult stem-cell-derived human colonoid monolayers (HCM) to test whether EHEC-secreted extracellular serine protease P (EspP), a member of the serine protease family broadly expressed by diarrheagenic E. coli can act as an enterotoxin. We applied the Ussing chamber/voltage clamp technique to determine whether EspP stimulates electrogenic ion transport indicated by a change in short-circuit current (Isc). EspP stimulates Isc in HCM. The EspP-stimulated Isc does not require protease activity, is not cystic fibrosis transmembrane conductance regulator (CFTR)-mediated, but is partially Ca2+-dependent. EspP neutralization with a specific antibody reduces its potency in stimulating Isc. Serine Protease A, secreted by Enteroaggregative E. coli, also stimulates Isc in HCM, but this current is CFTR-dependent. In conclusion, EspP stimulates colonic CFTR-independent active ion transport and may be involved in the pathophysiology of EHEC diarrhea. Serine protease toxins from E. coli pathogens appear to serve as enterotoxins, potentially significantly contributing to watery diarrhea.

Bioelectric properties and ion flow across excised human bronchi

1984 ◽  
Vol 56 (4) ◽  
pp. 868-877 ◽  
Author(s):  
M. Knowles ◽  
G. Murray ◽  
J. Shallal ◽  
F. Askin ◽  
V. Ranga ◽  
...  
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Maximal Effect ◽  
Na Transport ◽  
Adrenergic Agents ◽  
Ion Flow ◽  
Cl Secretion ◽  
Active Ion Transport ◽  
Human Bronchi

Bioelectric properties and ion transport of excised human segmental/subsegmental bronchi were measured in specimens from 40 patients. Transepithelial electric potential difference (PD), short-circuit current (Isc), and conductance (G), averaged 5.8 mV (lumen negative), 51 microA X cm-2, and 9 mS X cm-2, respectively. Na+ was absorbed from lumen to interstitium under open- and short-circuit conditions. Cl- flows were symmetrical under short-circuit conditions. Isc was abolished by 10(-4) M ouabain. Amiloride inhibited Isc (the concentration necessary to achieve 50% of the maximal effect = 7 X 10(-7) M) and abolished net Na+ transport. PD and Isc were not reduced to zero by amiloride because a net Cl- secretion was induced that reflected a reduction in Cl- flow in the absorptive direction (Jm----sCl-). Acetylcholine (10(-4) M) induced an electrically silent, matched flow of Na+ (1.7 mueq X cm-1 X h-1) and Cl- (1.9 mueq X cm-12 X h-1) toward the lumen. This response was blocked by atropine. Phenylephrine (10(-5) M) did not affect bioelectric properties or unidirectional ion flows, whereas isoproterenol (10(-5) M) induced a small increase in Isc (10%) without changing net ion flows significantly. We conclude that 1) Na+ absorption is the major active ion transport across excised human bronchi, 2) Na+ absorption is both amiloride and ouabain sensitive, 3) Cl- secretion can be induced by inhibition of the entry of luminal Na+ into the epithelia, and 4) cholinergic more than adrenergic agents modulate basal ion flow, probably by affecting gland output.

Dantrolene and basal ileal sodium and chloride transport: involvement of calcium stores

1983 ◽  
Vol 245 (6) ◽  
pp. G780-G785
Author(s):  
M. Donowitz ◽  
S. Cusolito ◽  
L. Battisti ◽  
G. W. Sharp
Keyword(s):  
Ion Transport ◽  
Intracellular Calcium ◽  
Chloride Transport ◽  
Short Circuit ◽  
Ussing Chamber ◽  
Short Circuit Current ◽  
Calcium Stores ◽  
Ionophore A23187 ◽  
Rabbit Ileum ◽  
Intracellular Calcium Stores

The effect of dantrolene on active ion transport in rabbit ileum was determined using the Ussing chamber short-circuiting technique. Dantrolene prevents the release of calcium from intracellular stores in skeletal muscle and was used to probe the role of intracellular calcium stores in intestinal ion transport. A saturated solution of dantrolene (approx 25 microM) decreased ileal short-circuit current and potential difference, increased conductance and mucosal-to-serosal and net Na and Cl fluxes, but did not alter serosal-to-mucosal Na and Cl fluxes. The dantrolene stimulation of active Na and Cl absorption was specific since it did not alter glucose-dependent Na absorption, transport changes caused by Ca2+ ionophore A23187, or the increase in short-circuit current caused by dibutyryl cAMP or theophylline. These effects were associated with an increase in total ileal calcium content and a decreased rate of 45Ca2+ efflux without any change in 45Ca2+ influx from the serosal or mucosal surfaces. These findings are consistent with an effect of dantrolene to stimulate active ileal Na and Cl absorption by a mechanism involving lowered cytosol Ca2+ levels and compatible with trapping calcium in intracellular stores. It thus appears as if intracellular calcium stores have an important role in the control of basal ion transport in the intestine.

Mast cells in the regulation of intestinal electrolyte transport

1986 ◽  
Vol 251 (2) ◽  
pp. G253-G262 ◽  
Author(s):  
D. A. Russell
Keyword(s):  
Mast Cells ◽  
Ion Transport ◽  
Trichinella Spiralis ◽  
Short Circuit ◽  
Ussing Chamber ◽  
Short Circuit Current ◽  
Antigen Challenge ◽  
Intracellular Camp ◽  
Camp Content ◽  
Ionic Basis

Experiments were performed to determine the ionic basis and physiological messengers of transepithelial ion transport alterations (short-circuit current, Isc) measured during the induction of intestinal anaphylaxis in an Ussing chamber. Antigens derived from Trichinella spiralis, an intestinal parasite, were used to challenge jejunal tissue from guinea pigs immunized by infection with the parasite. Histamine (10(-4) M) caused an increased in Isc that was similar to that induced by antigen. Diphenhydramine (10(-5) M) inhibited the epithelial electrical responses to histamine by 100% and to antigen by 60-70%. Indomethacin (10(-5) M), in combination with diphenhydramine, completely inhibited the antigen-induced rise in Isc. Furosemide (10(-4) M) caused 50-60% inhibition of the increase in Isc induced by antigen and histamine. Antigen challenge of isolated enterocytes did not alter intracellular cAMP content. However, antigen challenge of jejunal segments in which epithelial cells were in contact with sensitized mast cells increased mucosal cAMP content. These results suggest that electrogenic Cl- secretion, mediated in part by cAMP, contributes to antigen-induced jejunal ion transport changes and that histamine and prostaglandins are involved in eliciting these epithelial responses.

Effects of carbon monoxide on ion transport across rat distal colon

2011 ◽  
Vol 300 (2) ◽  
pp. G207-G216 ◽  
Author(s):  
Julia Steidle ◽  
Martin Diener
Keyword(s):  
Carbon Monoxide ◽  
Ion Transport ◽  
Short Circuit ◽  
Ussing Chamber ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Disulfonic Acid ◽  
Maximal Response ◽  
Colonic Crypts ◽  
Acid Sodium Salt

The aim of the present study was to investigate whether carbon monoxide (CO) induces changes in ion transport across the distal colon of rats and to study the mechanisms involved. In Ussing chamber experiments, tricarbonyldichlororuthenium(II) dimer (CORM-2), a CO donor, evoked a concentration-dependent increase in short-circuit current ( Isc). A maximal response was achieved at a concentration of 2.5·10−4 mol/l. Repeated application of CORM-2 resulted in a pronounced desensitization of the tissue. Anion substitution experiments suggest that a secretion of Cl− and HCO3− underlie the CORM-2-induced current. Glibenclamide, a blocker of the apical cystic fibrosis transmembrane regulator channel, inhibited the Isc induced by the CO donor. Similarly, bumetanide, a blocker of the basolateral Na+-K+-2Cl− cotransporter, combined with 4-acetamido-4′-isothiocyanato-stilbene-2,2′-disulfonic acid sodium salt, an inhibitor of the basolateral Cl−/HCO3− exchanger, inhibited the CORM-2-induced Isc. Membrane permeabilization experiments indicated an activation of basolateral K+ and apical Cl− channels by CORM-2. A partial inhibition by the neurotoxin, tetrodotoxin, suggests the involvement of secretomotor neurons in this response. In imaging experiments at fura-2-loaded colonic crypts, CORM-2 induced an increase of the cytosolic Ca2+ concentration. This increase depended on the influx of extracellular Ca2+, but not on the release of Ca2+ from intracellular stores. Both enzymes for CO production, heme oxygenase I and II, are expressed in the colon as observed immunohistochemically and by RT-PCR. Consequently, endogenous CO might be a physiological modulator of colonic ion transport.

Changes in midgut active ion transport and metabolism during larval-larval molting in the tobacco hornworm (Manduca sexta)

1997 ◽  
Vol 200 (3) ◽  
pp. 643-648 ◽  
Author(s):  
M Chamberlin ◽  
C Gibellato ◽  
R Noecker ◽  
E Dankoski
Keyword(s):  
Ion Transport ◽  
Manduca Sexta ◽  
Aerobic Capacity ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Tobacco Hornworm ◽  
Maximal Aerobic Capacity ◽  
Posterior Midgut ◽  
Molting Process ◽  
Active Ion Transport

Ion transport and metabolism in the posterior midgut before, during and after the molt to the fifth instar of the tobacco hornworm Manduca sexta were investigated. In situ measurements reveal that the transepithelial potential difference of the posterior midgut falls during the molting process. This finding was confirmed by in vitro experiments in which it was demonstrated that both the transepithelial potential and the short-circuit current are lower in molting fourth instars compared with feeding fourth instars. The short-circuit current increases after ecdysis, with a maximal rate being achieved approximately 4 h after the molt. Resumption of feeding after the molt is not necessary to initiate this increase in active ion transport. The metabolic organization of the tissue also changes during the molting process. The maximal activities of glycolytic enzymes and 3-hydroxyacyl-CoA dehydrogenase, an enzyme of lipid ss-oxidation, decrease during the molting process and increase after ecdysis. Although citrate synthase activity, an index of maximal aerobic capacity, decreases during the molt and increases again after ecdysis, tissue respiration is the same in feeding fourth instars and molting larvae. This result indicates that a greater percentage of maximal aerobic capacity is used during molting and that energy may be diverted to cell proliferation and differentiation and away from the support of active ion transport at this time.

Primary culture of duck salt gland. II. Neurohormonal stimulation of active transport

1985 ◽  
Vol 249 (1) ◽  
pp. C41-C47 ◽  
Author(s):  
R. J. Lowy ◽  
D. C. Dawson ◽  
S. A. Ernst
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Primary Cultures ◽  
Short Circuit Current ◽  
Salt Gland ◽  
Hormonal Control ◽  
Regulatory Control ◽  
Secretory Cells ◽  
Active Ion Transport ◽  
Secretory Transport

Primary cultures of structurally polarized sheets of avian salt gland secretory cells were mounted in Lucite chambers for transmural electrophysiological analysis. Transmural resistance values increased during the first 3 days of culture to 293 +/- 35 omega X cm2 and then decreased slowly thereafter. There was little short-circuit current (Isc) in the absence of secretagogues. Serosal addition of either carbachol or epinephrine resulted in a Isc consistent with positive charge flow from mucosa to serosa, thus demonstrating that these cell layers were capable of active ion transport in response to either cholinergic or adrenergic neurohormonal stimulation. Serosal ouabain or furosemide abolished the response to either agonist, while theophylline enhanced the response. Receptor specificity for the electrical responses was shown by selective inhibition of carbachol- and epinephrine-induced Isc by atropine and propranolol, respectively. The results demonstrate that these primary epithelial cell cultures are capable of active ion transport and are sensitive to known inhibitors of secretory transport, and suggest that intracellular coupling mechanisms for hormonal control are retained in culture. These cultures should be useful for studying mechanisms of ion secretory transport and their regulatory control.

Enteropathogenic E. coli attenuates secretagogue-induced net intestinal ion transport but not Cl− secretion

1999 ◽  
Vol 276 (3) ◽  
pp. G781-G788 ◽  
Author(s):  
Gail Hecht ◽  
Athanasia Koutsouris
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Transport Processes ◽  
Intestinal Epithelial ◽  
Cell Monolayers ◽  
E Coli ◽  
Ion Secretion ◽  
Dependent Transport ◽  
Intestinal Ion Transport

Enteric bacterial pathogens often increase intestinal Cl− secretion. Enteropathogenic Escherichia coli(EPEC) does not stimulate active ion secretion. In fact, EPEC infection decreases net ion transport in response to classic secretagogues. This has been presumed to reflect diminished Cl− secretion. The aim of this study was to investigate the influence of EPEC infection on specific intestinal epithelial ion transport processes. T84 cell monolayers infected with EPEC were used for these studies. EPEC infection significantly decreased short-circuit current ( I sc) in response to carbachol and forskolin, yet125I efflux studies revealed no difference in Cl− channel activity. There was also no alteration in basolateral K+ channel or Na+-K+-2Cl−cotransport activity. Furthermore, net36Cl−flux was not decreased by EPEC. No alterations in either K+ or Na+ transport could be demonstrated. Instead, removal of basolateral bicarbonate from uninfected monolayers yielded an I sc response approximating that observed with EPEC infection, whereas bicarbonate removal from EPEC-infected monolayers further diminished I sc. These studies suggest that the reduction in stimulated I sc is not secondary to diminished Cl−secretion. Alternatively, bicarbonate-dependent transport processes appear to be perturbed.

scholarly journals Segment-specific effects of epinephrine on ion transport in the colon of the rat

1998 ◽  
Vol 275 (6) ◽  
pp. G1367-G1376 ◽  
Author(s):  
Silke Hörger ◽  
Gerhard Schultheiß ◽  
Martin Diener
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Ussing Chamber ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Proximal Colon ◽  
Rat Colon ◽  
Second Phase ◽  
Stimulatory Action ◽  
Β Receptor

The effect of epinephrine on transport of K+, Na+, Cl−, and[Formula: see text] across the rat colon was studied using the Ussing chamber technique. Epinephrine (5 × 10−6mol/l) induced a biphasic change in short-circuit current ( Isc) in distal and proximal colon: a transient increase followed by a long-lasting decay. The first phase of the Iscresponse was abolished in Cl−-poor solution or after bumetanide administration, indicating a transient induction of Cl−secretion. The second phase of the response to epinephrine was suppressed by apical administration of the K+channel blocker, quinine, and was concomitant with an increase in serosal-to-mucosal Rb+flux, indicating that epinephrine induced K+secretion, although this response was much smaller than the change in Isc. In addition, the distal colon displayed a decrease in mucosal-to-serosal and serosal-to-mucosal Cl−fluxes when treated with epinephrine. In the distal colon, indomethacin abolished the first phase of the epinephrine effect, whereas the second phase was suppressed by TTX. In the proximal colon, indomethacin and TTX were ineffective. The neuronally mediated response to epinephrine in the distal colon was suppressed by the nonselective β-receptor blocker, propranolol, and by the β2-selective blocker, ICI-118551, whereas the epithelial response in the proximal colon was suppressed by the nonselective α-blocker, phentolamine, and by the selective α2-blocker, yohimbine. These results indicate a segment-specific action of epinephrine on ion transport: a direct stimulatory action on epithelial α2-receptors in the proximal colon and an indirect action on secretomotoneurons via β2-receptors in the distal colon.

Cadmium-induced Inhibition of ADH-stimulated Ion Transport in Cultured Kidney-derived Epithelial Cells (A6)

1997 ◽  
Vol 25 (3) ◽  
pp. 271-277
Author(s):  
Henning F. Bjerregaard ◽  
Brian Faurskov
Keyword(s):  
Epithelial Cells ◽  
Adenylate Cyclase ◽  
Ion Transport ◽  
Hormonal Regulation ◽  
Short Circuit ◽  
Distal Tubule ◽  
Short Circuit Current ◽  
Epithelial Cell Line ◽  
Active Ion Transport ◽  
Camp Metabolism

An epithelial cell line (A6) derived from the distal tubule of toad kidney, was used to study the effect of cadmium (Cd2+) on the increase in active ion transport induced by antidiuretic hormone (ADH). Addition of Cd2+ (1mM) to the basolateral solution of A6 epithelia generated an immediate and transient increase in active ion transport, measured as short circuit current (SCC). This increase was not affected by prior addition of ADH. However, there was a distinct inhibition of ADH-induced stimulation of SCC in epithelia pre-treated with Cd2+. Since cAMP serves as an intracellular messenger for ADH by increasing the ion permeability of the apical membrane in A6 epithelial cells, the effects of Cd2+ on enzymes involved in cAMP metabolism were measured. The results showed that Cd2+ markedly inhibits cAMP production by inhibiting adenylate cyclase (which had been stimulated with forskolin, magnesium or a non-hydrolysed GTP-analog), indicating that Cd2+ inhibits the catalytic subunit of adenylate cyclase. Furthermore, degradation of cAMP by phosphodiesterase was not stimulated by Cd2+, also suggesting that the mechanism by which Cd2+ inhibits the ADH-induced ion transport could be through inhibition of adenylate cyclase. Taken together, these results indicate that, in addition to the well-known toxic effect on the proximal tubule, Cd2+ could also have an effect on the distal part of the kidney, where the important hormonal regulation of salt and water homeostasis takes place.

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