Aldosterone modulates electrogenic Cl secretion in the colon of the hen (Gallus domesticus)

1991 ◽  
Vol 261 (6) ◽  
pp. R1533-R1541 ◽  
Author(s):  
W. Clauss ◽  
V. Dantzer ◽  
E. Skadhauge
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Na Channel ◽  
Na Transport ◽  
Electrogenic Transport ◽  
Ussing Chambers ◽  
Cl Secretion ◽  
Cotransport System ◽  
Hormonal Stimulus

The regulation of Na and Cl transport in hen colon by mineralocorticoids was investigated with isolated epithelia in vitro by histological and electrophysiological techniques. The electrogenic transport of Na and Cl was measured in Ussing chambers by the short-circuit current technique and was identified by the specific inhibitors amiloride and bumetanide or by the secretagogue theophylline. Hens were maintained either on low (LS)- or on high-NaCl diets (HS), and the plasma aldosterone (PA) levels of these groups were measured with radioimmunoassay. A group of HS hens received injections of aldosterone at a 6-h schedule before experiments. A group of LS hens was resalinated, and experiments were carried out at a 24-h interval for up to 3 days after resalination. The LS diet stimulated PA levels ninefold, compared with HS hens. Na transport was modulated by the hormonal stimulus in a way that the apical Na entry switched from an electrogenic Na-amino acid-hexose cotransport system completely to an amiloride-sensitive Na channel. Electrogenic Cl secretion was induced by theophylline and was inhibited by bumetanide. NaCl deprivation, resalination or aldosterone injection modulated electrogenic Cl secretion in parallel between 7 (HS) and 14.4 mu eq.cm-2.h-1 (LS), with pronounced alteration in tissue conductance. These findings reveal a new action of aldosterone that, besides stimulating Na absorption, also directly or indirectly modulates Cl secretion.

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.

Avian cecum: role of glucose and volatile fatty acids in transepithelial ion transport

1991 ◽  
Vol 260 (5) ◽  
pp. G703-G710 ◽  
Author(s):  
B. R. Grubb
Keyword(s):  
Fatty Acids ◽  
Ion Transport ◽  
Volatile Fatty Acids ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Serosal Side ◽  
Na Transport ◽  
Cl Secretion ◽  
Mucosal Side

In the fowl cecum in vitro, the influence of glucose and the three most prevalent naturally occurring volatile fatty acids (acetate, propionate, butyrate) on short-circuit current (Isc), electrical resistance, and transport of Na and Cl was determined. When glucose, acetate, or butyrate was present, ion transport was characterized by electrogenic Na absorption, greater than 65% of which was amiloride inhibitable, and Cl secretion, which also was electrogenic. Isc could be completely accounted for by net fluxes of Na and Cl. When glucose, acetate, or butyrate (10 mM both sides) was included in the incubation medium, cecal tissue maintained its Isc and a constant rate of net Na absorption and Cl secretion for a 5-h period. When no substrate was present or propionate was included in the medium, a marked fall in Isc and net Na and Cl fluxes was seen. Glucose caused an increase in Isc when added only to the serosal side. As 3-O-methylglucose (not metabolized) was not effective in stimulating Isc of the cecum (serosal or mucosal addition), it appeared that glucose increased Isc by acting as an energy substrate for active Na transport. Acetate and butyrate appeared to be equally effective in stimulating Na transport and Isc when placed on either side of the membrane. When the preparation was supplied with glucose (serosal side) and acetate was added to the mucosal side, no further stimulation of Isc occurred. Thus it appeared that acetate and butyrate were acting as substrates for active Na transport rather than stimulating Na transport by some other mechanism such as a cotransport with Na.(ABSTRACT TRUNCATED AT 250 WORDS)

Apical nonspecific cation conductances in rabbit cecum

1994 ◽  
Vol 266 (3) ◽  
pp. G475-G484 ◽  
Author(s):  
J. H. Sellin ◽  
W. P. Dubinsky
Keyword(s):  
Epithelial Transport ◽  
Apical Membrane ◽  
Divalent Cations ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Na Channel ◽  
Similar Response ◽  
Electrogenic Transport

Rabbit cecum exhibits electrogenic Na absorption in vitro. However, because this transport process is not inhibited by amiloride nor does it demonstrate saturation kinetics typical of the amiloride-inhibitable Na channel, we considered whether the cecal transporter represented one of a recently described family of nonselective cation conductances or channels (NSCC). Both transepithelial and vesicle studies demonstrated that K, Cs, and Rb were transported via an apical conductance. Electrogenic transport was inhibited by divalent cations including Ca, Mg, and Ba but was unaffected by either lanthanum or gadolinium. Parallel studies in distal colon did not exhibit a similar response to either K substitution or Ba inhibition. Phenamil, verapamil, and nicardipine significantly inhibited the short-circuit current (Isc). stimulated by nominal Ca- and Mg-free conditions. Flux studies demonstrated a correlation between changes in Isc and Na transport. Microelectrode impalement studies suggested that there may be both NSCC and K conductance in the apical membrane. Planar bilayer studies identified a 190-pS cation channel that may correlate with the macroscopic transport properties of this epithelium. These studies are consistent with a model of cecal Na absorption mediated by a NSCC in the apical membrane; this may be the mechanism underlying the distinct epithelial transport characteristics of this intestinal segment.

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.

In vitro studies of sodium transport across the lower intestine of a desert parrot

1980 ◽  
Vol 239 (3) ◽  
pp. R285-R290
Author(s):  
E. Skadhauge ◽  
T. J. Dawson
Keyword(s):  
Short Circuit ◽  
Electrical Potential ◽  
Flux Ratio ◽  
Short Circuit Current ◽  
Electrical Potential Difference ◽  
Na Transport ◽  
Salt Loading ◽  
Ussing Chambers ◽  
Lower Intestine

The lower intestine (coprodeum and colon) of the Australian parrot, the galah, was mounted in Ussing chambers. Short-circuit current (SCC), electrical potential difference (PD), and unidirectional fluxes of Na and Cl were measured in birds that were fed mixed seeds or were NaCl loaded. The net Na transport of both coprodeum and colon was nearly equal to the SCC, and the flux ratio for Cl was unity. In birds which received mixed seeds, average coprodeal Na transport was 7.8 mu eq . cm-2 . h-1, and PD was 19 mV. The Km for Na was 5.7 meq/l. In colon, Na transport was reduced by 67% and PD by 70%. The ratio between unidirectional Na and Cl fluxes in the serosa-mucosa direction was 0.7. Salt loading suppressed coprodeal, but increased colonic Na transport. The coprodeal and colonic SCC and NA transport of birds receiving mixed seeds were inhibited by amiloride on the mucosal side. Colonic SCC of NaCl-loaded birds was only slightly reduced by amiloride (by 17%), but stimulated by amino acids (by 18%).

Effect of sulfidopeptide leukotrienes D4 and E4 on ileal ion transport in vitro in the rat and rabbit

1988 ◽  
Vol 255 (2) ◽  
pp. G175-G183 ◽  
Author(s):  
P. L. Smith ◽  
D. P. Montzka ◽  
G. P. McCafferty ◽  
M. A. Wasserman ◽  
J. D. Fondacaro
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Bathing Solution ◽  
Na Transport ◽  
Rabbit Ileum ◽  
Rat Ileum ◽  
Ussing Chambers ◽  
Meclofenamic Acid ◽  
Acid Metabolites

Effects of leukotrienes D4 and E4 (LTD4 and LTE4) on electrolyte transport were examined, employing stripped segments of rat and rabbit ileum mounted in Ussing chambers. Addition of LTD4 or LTE4 to the serosal but not the mucosal bathing solution elicited a transient increase in short-circuit current (Isc) with maximal responses seen at 10(-5) M and 10(-8) M in rat and rabbit respectively and a sustained decrease in transepithelial conductance (Gt) in the rat only. In the rat, Cl replacement, reduction of bathing solution [Ca2+] to 1 microM or pretreatment with 1 microM indomethacin or meclofenamic acid inhibited the LTD4- or LTE4-induced Isc changes with no effect on the decrease in Gt. LTD4 (10 microM) transiently increased net Cl secretion and produced a sustained decrease in both unidirectional and net Na transport and mucosal-to-serosal Cl flux in rat ileum. The decrease in unidirectional Na fluxes is accounted for predominantly by a change in the potential independent flux of Na. These results suggest that the increase in Isc in both rat and rabbit is mediated by arachidonic acid metabolites, whereas the decrease in Gt and net Na absorption in rat ileum is mediated by a cyclooxygenase-independent pathway.

Ba2+ inhibition of VIP- and A23187-stimulated Cl- secretion by T84 cell monolayers

1986 ◽  
Vol 250 (3) ◽  
pp. C486-C494 ◽  
Author(s):  
K. G. Mandel ◽  
J. A. McRoberts ◽  
G. Beuerlein ◽  
E. S. Foster ◽  
K. Dharmsathaphorn
Keyword(s):  
Vasoactive Intestinal Polypeptide ◽  
Apical Membrane ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Short Circuit Current ◽  
Ussing Chambers ◽  
Cell Monolayers ◽  
Cl Secretion ◽  
Cotransport System ◽  
Permeable Supports

Addition of either 10(-8) M vasoactive intestinal polypeptide (VIP) or 10(-6) M A23187 to T84 cell monolayers, grown on permeable supports and mounted in Ussing chambers, stimulated net Cl- secretion. The effect of 10(-6) M A23187 on Cl- flux was consistently smaller than that observed with 10(-8) M VIP. In both cases the increase in net Cl- secretion accounted for the entire change in the observed short-circuit current (Isc). Since Cl- enters the cells through a basolaterally localized Na+-K+-Cl(-)-cotransport system (J. Clin. Invest. 75: 462, 1985), the fate of K+, which is cotransported with Cl- during VIP, and A23187-mediated Cl- secretion was explored. Unidirectional and net transepithelial 42K+ flux rates were negligible compared with 36Cl- flux rates (less than 4% of Cl- flux), indicating that little K+ was secreted along with Cl-. K+ recycling across the basolateral membrane was suggested from experiments in which 86Rb+ efflux (as a tracer for K+) was measured across the apical and basolateral membranes of 86Rb+ -preloaded monolayers under voltage-clamped conditions. In the absence of secretagogues, 86Rb+ efflux was 10-fold higher across the basolateral membrane than across the apical membrane. 86Rb+ efflux across the basolateral membrane was accelerated two- to threefold by addition of either VIP or A23187. In each case accelerated efflux was inhibited by 5 mM Ba2+. Cl- secretion induced by VIP or A23187 was also inhibited by serosal addition of Ba2+.(ABSTRACT TRUNCATED AT 250 WORDS)

Interaction between sodium and chloride transport in canine tracheal mucosa

1979 ◽  
Vol 46 (1) ◽  
pp. 111-119 ◽  
Author(s):  
F. J. Al-Bazzaz ◽  
Q. Al-Awqati
Keyword(s):  
Hormonal Regulation ◽  
Chloride Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Na Transport ◽  
Tracheal Mucosa ◽  
Electrically Conductive ◽  
Ussing Chambers ◽  
Cl Secretion ◽  
Cl Transport

Canine tracheal mucosae were dissected and mounted as flat sheets in Ussing chambers. Unidirectional isotope fluxes of 22Na and 36Cl were performed across paired mucosae from the same animal. The average spontaneous potential difference was 42 + 1.2 mV (mean +/- SE) lumen negative. The short-circuit current (SCC) 3.09 +/- 0.36 mueq/cm2.h was accounted for by a net Cl secretion of 2.46 +/- 0.26 mueq/cm2.h toward the mucosa and net Na absorption of 0.46 +/- 0.13 mueq/cm2.h toward submucosa. Removal of Cl depressed SCC but had no effect on unidirectional or net Na transport (n = 7). By contrast, removal of Na (n = 6) or the addition of ouabain (n = 7) abolished net Cl secretion and greatly reduced SCC. Theophylline (n = 6) added to the submucosal bath no significant effect on Na transport but stimulated SCC and Cl secretion, suggesting hormonal regulation of Cl transport. The results suggest that the active transport of Na and Cl in this epithelium occur by electrically conductive pathways, i.e., the transport is “electrogenic.” Further it appears that Na transport is independent of the presence of Cl but that Cl transport depends on some parameter of active Na transport.

Colonic potassium and chloride secretion: role of cAMP and calcium

1985 ◽  
Vol 248 (1) ◽  
pp. G103-G109 ◽  
Author(s):  
R. D. McCabe ◽  
P. L. Smith
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Chloride Secretion ◽  
Bathing Solution ◽  
Ionophore A23187 ◽  
Ussing Chambers ◽  
Cl Secretion ◽  
Intracellular Ca

Stripped rabbit colonic mucosa was studied in vitro in Ussing chambers to further investigate the role of Ca in regulating K and Cl secretion stimulated by the divalent cation ionophore A23187, prostaglandin E1 (PGE1), or 8-bromo-cAMP (8BrcAMP). To assess the effects of these secretagogues on the paracellular shunt permeability, we measured the Na concentration dependence of the serosal-to-mucosal Na flux in the absence or presence of these stimuli. Results from these studies reveal that changes in net K and Cl secretion produced by secretory stimuli cannot be accounted for by a change in shunt permeability. The possible involvement of Ca in the secretory response of the colon to these stimuli was investigated by measuring the changes in Cl and K transport elicited by A23187, PGE1, or 8BrcAMP in the absence or presence of trifluoperazine (10(-4) M) added to the serosal bathing solution. Trifluoperazine alone did not significantly alter basal Na or Cl fluxes or short-circuit current (Isc) but did decrease transepithelial conductance (Gt) and the serosal-to-mucosal K flux. Pretreatment of the tissues with trifluoperazine significantly reduced or abolished the changes in K fluxes elicited by A23187, 8BrcAMP, or PGE1 without altering the changes in Cl transport, Isc, and Gt. These results suggest that K secretion induced by these secretagogues involves an increase in intracellular Ca concentration and may be mediated by calmodulin.

Serotonin induces Cl- secretion in human jejunal mucosa in vitro via a nonneural pathway at a 5-HT4 receptor

1994 ◽  
Vol 267 (3) ◽  
pp. G357-G363 ◽  
Author(s):  
J. M. Kellum ◽  
M. R. Budhoo ◽  
A. K. Siriwardena ◽  
E. P. Smith ◽  
S. A. Jebraili
Keyword(s):  
Gastric Bypass Surgery ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Cholinergic Receptor ◽  
Jejunal Mucosa ◽  
Receptor Antagonists ◽  
Ussing Chambers ◽  
Cl Secretion ◽  
Ics 205 930

We examined the effect of 5-hydroxytryptamine (5-HT) on Na+ and Cl- flux (J) and short-circuit current (Isc) in human jejunal mucosa. Segments of jejunum, taken at the time of gastric bypass surgery, were stripped of the seromuscular layers (and attached neural ganglia) and mounted as flat mucosal sheets in Ussing chambers under short-circuit conditions. 5-HT (0.1-100 microM) produced a concentration-dependent rise in Isc (mean effective concn = 2.5 microM). Using 22Na and 36Cl, we measured flux across control tissues and in those exposed to 5-HT. 5-HT decreased both net JNa and JCl and increased Isc (-1.1 +/- 0.6, -1.7 +/- 0.6, and 0.6 +/- 0.1 mueq.cm-2.h-1, respectively). Thus the 5-HT-induced rise in Isc could be accounted for by reduced net JNa and JCl. 5-HT induced a significant (P < 0.05) Cl- secretion (serosal-to-mucosal flux) when glucose was included in the buffer bathing the mucosal surface. Neither tetrodotoxin, the adrenergic receptor antagonists prazosin and propranolol, nor the cholinergic receptor antagonists atropine and hexamethonium inhibited the change (delta) in Isc induced by 5-HT. 5-Methoxytryptamine (5-MeOT) and zacopride, known 5-HT4 receptor agonists, induced significant delta Isc. The 5-HT receptor antagonists N-acetyl-5-hydroxytryptophyl-5-hydroxytryptamine (5-HT1P), ketanserin (5-HT2), and ICS-205-930 (preferential for 5-HT3 at 0.1 microM had no effect on delta Isc.(ABSTRACT TRUNCATED AT 250 WORDS)

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