Fasting alters basal and stimulated ion transport in piglet jejunum

1994 ◽  
Vol 267 (1) ◽  
pp. R156-R163 ◽  
Author(s):  
H. V. Carey ◽  
U. L. Hayden ◽  
K. E. Tucker
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Short Term ◽  
Ussing Chambers ◽  
Cl Secretion ◽  
Heat Stable ◽  
Active Ion Transport ◽  
Total Tissue ◽  
Net Fluxes

Three-week-old piglets were used to study the effects of short-term fasting on jejunal ion transport. A 48-h fast significantly reduced mucosal weight, villus height, and crypt depth. Fasting increased basal short-circuit current (Isc), which reflects active ion transport, and total tissue conductance (Gt) of muscle-stripped jejunal sheets mounted in Ussing chambers. Increases in Isc evoked by carbachol, serotonin, histamine, prostaglandin E2, or Escherichia coli heat-stable enterotoxin were significantly greater in the fasted piglets. Isc responses to mucosal D-glucose were also enhanced by the fast. Under basal conditions, unidirectional and net fluxes of Na+ and Cl-, as well as serosal-to-mucosal inulin fluxes, were significantly increased in fasted piglets. In fed piglets, carbachol increased net Cl- secretion by stimulating serosal-to-mucosal Cl- flux; Gt was not affected. In fasted piglets, carbachol increased net Cl- secretion by inhibiting mucosal-to-serosal fluxes with no effect on serosal-to-mucosal fluxes. In addition, carbachol significantly inhibited mucosal-to-serosal Na+ fluxes and reduced Gt in this group. Thus a 48-h fast increased unidirectional and net ion fluxes in piglet jejunum and enhanced ion transport responses to secretory agonists. The mechanism by which carbachol stimulated net Cl- secretion was also altered by the fast. These results suggest that the absence of luminal nutrition changes the ion transport characteristics of the jejunal epithelium.

Ion transport across cat and ferret tracheal epithelia

1986 ◽  
Vol 61 (3) ◽  
pp. 1065-1070 ◽  
Author(s):  
R. J. Corrales ◽  
D. L. Coleman ◽  
D. B. Jacoby ◽  
G. D. Leikauf ◽  
H. L. Hahn ◽  
...  
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Free Medium ◽  
Mucin Secretion ◽  
Ussing Chambers ◽  
Cl Secretion ◽  
Mucosal Side

Sheets of trachea from ferret and cat were mounted in Ussing chambers and continuously short circuited. Under resting conditions, in both the cat and ferret there was little or no Cl secretion, and Na absorption accounted for most of the short-circuit current (Isc). Ouabain (10(-4) M, serosal bath) reduced Isc to zero in 30–60 min. This decline was matched by a decrease in net Na absorption. Amiloride (10(-4) M, luminal bath) caused a significant decrease in Isc and conductance (G) in both species. Bumetanide (10(-4) M, serosal bath) had negligible effects on Isc and G. In both species, isoproterenol increased Isc by stimulating Cl secretion. Methacholine induced equal amounts of Na and Cl secretion, with little change in Isc. In the cat, prostaglandins E2 and F2 alpha and bradykinin increased Isc, responses which were abolished in Cl-free medium. In open-circuited cat tissues, Na flux from the serosal to mucosal side was measured simultaneously with the secretion of nondialyzable 35S. Prostaglandins E1, E2, and F2 alpha, histamine, bradykinin, methacholine and isoproterenol all increased both Na and 35S-mucin secretion.

Neuromodulation of ion transport in porcine distal colon: NPY reduces secretory actions of leukotrienes

1995 ◽  
Vol 269 (2) ◽  
pp. R426-R431 ◽  
Author(s):  
T. R. Traynor ◽  
D. R. Brown ◽  
S. M. O'Grady
Keyword(s):  
Ion Transport ◽  
Colonic Mucosa ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Effective Concentration ◽  
Leukotriene C4 ◽  
Ussing Chambers ◽  
Cl Secretion ◽  
Half Maximal Effective Concentration

Electrical transmural stimulation (ETS) was used to examine the neuroregulation of electrolyte transport in the porcine distal colon. ETS of the colonic mucosa-submucosa mounted in Ussing chambers produced rapid and transient increases in short-circuit current (Isc) that were inhibited 36% by serosal bumetanide, suggesting that a portion of the response may be attributed to Cl secretion. ETS actions were dependent upon stimulus intensity and frequency and were inhibited by tetrodotoxin and omega-conotoxin. Prazosin and pyrilamine had no effect on the mucosal responses to ETS, whereas atropine reduced the responses by 32%. Neuropeptide Y (NPY) also reduced the mucosal responses to ETS up to 60% (half-maximal effective concentration = 17 nM). In addition, the effects of leukotriene C4, previously shown to stimulate Cl secretion via a neuronal pathway, were also inhibited by NPY. These results indicate that cholinergic submucosal neurons play a role in the regulation of epithelial ion transport and that NPY acts as an inhibitory neuromodulator, particularly on leukotriene-sensitive neurons in the porcine distal colon.

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.

NaCl transport across equine proximal colon and the effect of endogenous prostanoids

1990 ◽  
Vol 259 (1) ◽  
pp. G62-G69 ◽  
Author(s):  
L. L. Clarke ◽  
R. A. Argenzio
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Proximal Colon ◽  
Nacl Transport ◽  
Apparent Lack ◽  
Ussing Chambers ◽  
Cl Secretion

In contrast to in vivo findings, the equine proximal colon fails to demonstrate significant net absorption of Na+ and Cl- under in vitro conditions. The present study was undertaken to determine if endogenous prostanoids are responsible for this apparent lack of ion transport. Proximal colonic tissues from ponies were preincubated in either normal Ringer solution or in Ringer containing 1 microM indomethacin and studied in Ussing chambers containing these solutions. Untreated colonic mucosa demonstrated negligible Na(+)-Cl- absorption in the basal state. In contrast, indomethacin-treated colon significantly absorbed Na+ and Cl-, primarily as the result of an equivalent increase in the mucosal-to-serosal flux of these ions. Preincubation of proximal colon in 0.1 mM ibuprofen-treated Ringer yielded similar results. Treatment of indomethacin colon with 1 mM mucosal amiloride eliminated net Na(+)-Cl- absorption without affecting the short-circuit current (Isc). The Isc in control tissue was significantly greater than in indomethacin-treated tissue and was reduced by 0.1 mM serosal furosemide. Serosal addition of 0.1 microM prostaglandin E2 or 10 mM serosal plus mucosal theophylline to indomethacin-treated tissues abolished net Na(+)-Cl- absorption and increased the Isc to levels indistinguishable from control. In contrast, control tissues were essentially unaffected by these secretagogues. These findings indicated that Na(+)-Cl- absorption in equine proximal colon was electroneutral (possibly involving Na(+)-H+ exchange) and that the tissue was capable of electrogenic Cl- secretion. However, under the in vitro conditions, basal ion transport was dominated by endogenous prostanoids that abolished Na(+)-Cl- absorption and elicited near-maximal electrogenic Cl- secretion.

Electrolyte transport in rabbit cecum. I. Effect of RDEC-1 infection

1989 ◽  
Vol 256 (4) ◽  
pp. G721-G726 ◽  
Author(s):  
Y. H. Tai ◽  
T. P. Gage ◽  
C. McQueen ◽  
S. B. Formal ◽  
E. C. Boedeker
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Fluid Secretion ◽  
Coli Strain ◽  
High Rate ◽  
Ussing Chambers ◽  
Induced Changes ◽  
Tight Junction Disruption ◽  
Net Fluxes

To investigate the characteristics of intestinal ion and fluid secretion induced by the adherent, effacing enteropathogenic Escherichia coli strain RDEC-1, we infected weanling rabbits with 10(7)-10(8) RDEC-1 organisms and then studied cecal ion transport under short-circuit conditions in Ussing chambers. Results in tissues with confluent adherent organisms were compared with those in uninfected ceca and in ceca stimulated with dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP). The short-circuited cecum normally absorbed Na and Cl, secreted bicarbonate (as represented by the residual ion flux), and displayed a high rate of nondiffusional Na and Cl transport. RDEC-1 infection did not alter the short-circuit current (Isc), but it increased the conductance (Gt), decreased the potential difference (PD), abolished net Na absorption, and reversed Cl absorption to secretion. The changes in Na and Cl net fluxes may be explained by inhibition of a Na-Cl linked absorptive process. In contrast, DBcAMP significantly increased the Isc, PD, and Gt, decreased net Na flux, and abolished net Cl absorption by stimulating electrogenic Cl secretion. These results suggest that RDEC-1-induced changes in cecal ion transport are not mediated by cAMP. The reduction in Na-Cl linked absorption is consistent with anatomic changes in the apical surfaces of absorptive epithelial characteristic of effacing enteroadherence, whereas the increased conductance is consistent with tight junction disruption seen with RDEC-1 infection.

Taurodeoxycholate and the developing rabbit distal colon: absence of secretory effect

1987 ◽  
Vol 253 (4) ◽  
pp. G483-G488 ◽  
Author(s):  
G. D. Potter ◽  
R. Lester ◽  
S. M. Burlingame ◽  
P. A. Mitchell ◽  
K. L. Schmidt
Keyword(s):  
Ion Transport ◽  
Bile Acids ◽  
Phorbol Ester ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Fluid Secretion ◽  
Secretory Response ◽  
Ussing Chambers ◽  
Cl Secretion

Failure to absorb bile acids by the ileum leads to fluid secretion by the colon and diarrhea in adults. The infant ileum, however, does not actively transport bile acids. Therefore, we investigated the effect of taurodeoxycholic acid (TDCA) on ion transport in the colon of rabbits 7-10 days old. We mounted distal colon from infant and adult rabbits in modified Ussing chambers and exposed the mucosal or serosal surfaces to TDCA. In the adult, 50 microM TDCA produced an increase in short-circuit current (delta Isc = 1.0 +/- 0.3 mu eq . h-1 . cm-2, P less than 0.05) and Cl secretion. In the infant, the effect was different, Isc was reduced (delta Isc = -1.1 +/- 0.2 mu eq . h-1 . cm-2, P less than 0.01) and ion flux was not altered. Microscopy demonstrated that the infant epithelium was not significantly damaged by exposure to TDCA at these concentrations. The infant colon was, however, capable of a secretory response to a variety of agonists including theophylline, carbachol, bradykinin, serotonin, and 12,13-dibutyryl phorbol ester. The infant rabbit distal colon lacks a secretory response to TDCA during that period when the ileum cannot transport bile acids.

Effects of raised osmolarity on canine tracheal epithelial ion transport function

1987 ◽  
Vol 62 (6) ◽  
pp. 2241-2245 ◽  
Author(s):  
J. R. Yankaskas ◽  
J. T. Gatzy ◽  
R. C. Boucher
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Upper Airway ◽  
Short Circuit Current ◽  
Base Line ◽  
Cl Secretion ◽  
Parallel Increase ◽  
Active Ion Transport ◽  
Solution Bathing ◽  
Surface Liquid

Evaporation of water from upper airway surfaces increases surface liquid osmolarity. We studied the effects of raised osmolarity of the solution bathing the luminal surface of excised canine tracheal epithelium. Osmolarity was increased by adding NaCl or mannitol. NaCl addition induced a concentration-dependent fall in short-circuit current and a rise in transepithelial conductance (-33% and +14% per 100 mosM, respectively). Unidirectional isotopic fluxes of 22Na, 36Cl, and [14C]mannitol were measured in short-circuited tissues in the base-line state and after addition of NaCl or mannitol to an isotonic mucosal solution. NaCl addition (75 mM) caused a 50% increase in conductance (G) and a parallel increase in [14C]mannitol permeability (Pmann), indicating an increase in paracellular permeability. Net Cl- secretion was reduced 50%, and net Na+ absorption was unchanged despite an increased chemical gradient for absorption, indicating an inhibition of active ion transport. Mannitol addition (150 mM) abolished net Na+ absorption but did not increase G or Pmann or change net Cl- secretion. These results suggest that responses to increased tracheal surface liquid osmolarity during spontaneous breathing may occur in both the cellular (inhibition of active Na+ and Cl- transport) and paracellular (increased [14C]mannitol permeability) compartments of the mucosa.

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.

Active electrolyte transport in mammalian buccal mucosa

1988 ◽  
Vol 255 (3) ◽  
pp. G286-G291 ◽  
Author(s):  
R. C. Orlando ◽  
N. A. Tobey ◽  
V. J. Schreiner ◽  
R. D. Readling
Keyword(s):  
Buccal Mucosa ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Electrolyte Transport ◽  
Electrical Potential Difference ◽  
Ussing Chambers ◽  
Net Fluxes

The transmural electrical potential difference (PD) was measured in vivo across the buccal mucosa of humans and experimental animals. Mean PD was -31 +/- 2 mV in humans, -34 +/- 2 mV in dogs, -39 +/- 2 mV in rabbits, and -18 +/- 1 mV in hamsters. The mechanisms responsible for this PD were explored in Ussing chambers using dog buccal mucosa. After equilibration, mean PD was -16 +/- 2 mV, short-circuit current (Isc) was 15 +/- 1 microA/cm2, and resistance was 1,090 +/- 100 omega.cm2, the latter indicating an electrically "tight" tissue. Fluxes of [14C]mannitol, a marker of paracellular permeability, varied directly with tissue conductance. The net fluxes of 22Na and 36Cl were +0.21 +/- 0.05 and -0.04 +/- 0.02 mueq/h.cm2, respectively, but only the Na+ flux differed significantly from zero. Isc was reduced by luminal amiloride, serosal ouabain, or by reducing luminal Na+ below 20 mM. This indicated that the Isc was determined primarily by active Na+ absorption and that Na+ traverses the apical membrane at least partly through amiloride-sensitive channels and exits across the basolateral membrane through Na+-K+-ATPase activity. We conclude that buccal mucosa is capable of active electrolyte transport and that this capacity contributes to generation of the buccal PD in vivo.

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.

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