Cyclic nucleotide-gated cation channels mediate sodium and calcium influx in rat colon

2000 ◽  
Vol 278 (2) ◽  
pp. C336-C343 ◽  
Author(s):  
W. Qiu ◽  
B. Lee ◽  
M. Lancaster ◽  
W. Xu ◽  
S. Leung ◽  
...  
Keyword(s):  
Cyclic Nucleotide ◽  
Calcium Absorption ◽  
Calcium Influx ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Proximal Colon ◽  
Cation Channels ◽  
Rat Colon ◽  
Sodium Absorption

We found mRNA for the three isoforms of the cyclic nucleotide-gated nonselective cation channel expressed in the mucosal layer of the rat intestine from the duodenum to the colon and in intestinal epithelial cell lines in culture. Because these channels are permeable to sodium and calcium and are stimulated by cGMP or cAMP, we measured 8-bromo-cGMP-stimulated sodium-mediated short-circuit current ( I sc) in proximal and distal colon and unidirectional45Ca2+fluxes in proximal colon to determine whether these channels could mediate transepithelial sodium and calcium absorption across the colon. Sodium-mediated I sc, stimulated by 8-bromo-cGMP, were inhibited by dichlorobenzamil and l-cis-diltiazem, blockers of cyclic nucleotide-gated cation channels, suggesting that these ion channels can mediate transepithelial sodium absorption. Sodium-mediated I sc and net transepithelial45Ca2+absorption were stimulated by heat-stable toxin from Escherichia coli that increases cGMP. Addition of l-cis-diltiazem inhibited the enhanced transepithelial absorption of both ions. These results suggest that cyclic nucleotide-gated cation channels simultaneously increase net sodium and calcium absorption in the colon of the rat.

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.

Dietary flavonol quercetin induces chloride secretion in rat colon

1998 ◽  
Vol 275 (5) ◽  
pp. G1166-G1172 ◽  
Author(s):  
Rainer Cermak ◽  
Ursula Föllmer ◽  
Siegfried Wolffram
Keyword(s):  
Short Circuit ◽  
Ussing Chamber ◽  
Phosphodiesterase Inhibitor ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Chloride Secretion ◽  
Proximal Colon ◽  
Rat Colon ◽  
Quercetin Glycoside

The aim of this study was to investigate the possible effects of the flavonol quercetin, the most abundant dietary flavonoid, on the intestinal mucosa. In vitro experiments were performed with various segments of the rat intestine, using the Ussing chamber technique. Quercetin increased the short-circuit current ( I sc) in the jejunum, ileum, and proximal and distal colon. Additional experiments were performed using preparations of the proximal colon. The maximum effective dose of quercetin was found to be ∼100 μM. The quercetin-induced increase in I sc was inhibited by the Cl− channel blocker 5-nitro-2-(3-phenylpropylamino)-benzoic acid. Adding blockers of the Na+-K+-2Cl−cotransporter to the serosal compartment diminished the increase of I sc due to quercetin. Ion substitution and flux measurements indicated that the effect of quercetin was due to electrogenic Cl− and[Formula: see text] secretion. In contrast to the aglycone, the quercetin glycoside rutin had no effect. The effect of quercetin on I scwas additive to the I sc increase induced by forskolin, but the flavonoid diminished the I sc evoked by carbachol. The phosphodiesterase inhibitor theophylline blocked the effect of quercetin. Genistein, a related isoflavone, did not alter the I sc evoked by quercetin. These findings demonstrate that the dietary flavonol quercetin induces Cl−secretion and most likely [Formula: see text]secretion in rat small and large intestine. The effects are restricted to the flavonol aglycone.

Flupirtine enhances NHE-3 mediated Na+ absorption in rat colon via an ENS-dependent mechanism

2021 ◽  
Author(s):  
Andrew J. Nickerson ◽  
Vazhaikkurichi M. Rajendran
Keyword(s):  
Immunofluorescence Microscopy ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Proximal Colon ◽  
Selective Inhibitor ◽  
Rat Colon ◽  
Pre Treatment ◽  
Apical Membranes ◽  
Microscopy Techniques ◽  
Dependent Mechanism

Recent studies in our lab have shown that the KV7 channel activator, flupirtine, inhibits colonic epithelial Cl- secretion through effects on submucosal neurons of the enteric nervous system (ENS). We hypothesized that flupirtine would also stimulate Na+ absorption as a result of reduced secretory ENS input to the epithelium. To test this hypothesis, unidirectional 22Na+ fluxes were measured under voltage-clamped conditions. Pharmacological approaches using an Ussing-style recording chamber, combined immunofluorescence microscopy techniques were used to determine the effect of flupirtine on active Na+ transport in the rat colon. Flupirtine stimulated electroneutral Na+ absorption in partially seromuscular stripped colonic tissues, while simultaneously inhibiting short circuit current (ISC; i.e., Cl- secretion). Both of these effects were attenuated by pre-treatment with the ENS inhibitor, tetrodotoxin. The NHE-3-selective inhibitor, S3226, significantly inhibited flupirtine-stimulated Na+ absorption whereas the NHE-2-selective inhibitor HOE-694 did not. NHE-3 localization near the apical membranes of surface epithelial cells was also more apparent in flupirtine-treated colon versus control. Flupirtine did not alter epithelial Na+ channel (ENaC)-mediated Na+ absorption in distal colonic tissues obtained from hyperaldosteronaemic rats and had no effect in the normal ileum, but did stimulate Na+ absorption in the proximal colon. Finally, the parallel effects of flupirtine on ISC (Cl- secretion) and Na+ absorption were significantly correlated with each other. Together, these data indicate that flupirtine stimulates NHE-3-dependent Na+ absorption, likely as a result of reduced stimulatory input to the colonic epithelium by submucosal ENS neurons.

Corticosteroid alteration of active electrolyte transport in rat distal colon

1983 ◽  
Vol 245 (5) ◽  
pp. G668-G675 ◽  
Author(s):  
E. S. Foster ◽  
T. W. Zimmerman ◽  
J. P. Hayslett ◽  
H. J. Binder
Keyword(s):  
Colonic Mucosa ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Transport Processes ◽  
Electrolyte Transport ◽  
Sodium Absorption ◽  
Rat Distal Colon ◽  
Potassium Absorption ◽  
Potassium Secretion

To determine the effect of corticosteroids on active transport processes, unidirectional fluxes of 22Na, 36Cl, and 42K were measured under short-circuit conditions across isolated stripped distal colonic mucosa of the rat in control, secondary hyperaldosterone, and dexamethasone-treated animals. In controls net sodium and chloride fluxes (JNanet and JClnet) and short-circuit current (Isc) were 6.6 +/- 2.2, 7.6 +/- 1.6, and 1.3 +/- 0.2 mu eq X h-1 X cm-2, respectively. Although aldosterone increased Isc to 7.3 +/- 0.5 mu eq X h-1 X cm-2, JNanet (6.9 +/- 0.7 mu eq X h-1 X cm-2) was not altered and JClnet was reduced to 0 compared with controls. Dexamethasone also stimulated Isc but did not inhibit JClnet. In Cl-free Ringer both aldosterone and dexamethasone produced significant and equal increases in JNanet and Isc. Theophylline abolished JNanet in control animals but not in the aldosterone group. Aldosterone reversed net potassium absorption (0.58 +/- 0.11 mu eq X h-1 X cm-2) to net potassium secretion (-0.94 +/- 0.08 mu eq X h-1 X cm-2). Dexamethasone reduced net potassium movement to 0 (-0.04 +/- 0.12 mu eq X h-1 X cm-2). These studies demonstrate that 1) corticosteroids stimulate electrogenic sodium absorption and 2) aldosterone, but not dexamethasone, inhibits neutral NaCl absorption and stimulates active potassium secretion. The effects of mineralocorticoids and glucocorticoids on electrolyte transport are not identical and may be mediated by separate and distinct mechanisms.

Regulation of amiloride-sensitive electrogenic sodium transport in the rat colon by steroid hormones

1985 ◽  
Vol 248 (1) ◽  
pp. G124-G132 ◽  
Author(s):  
P. C. Will ◽  
R. N. Cortright ◽  
R. C. DeLisle ◽  
J. G. Douglas ◽  
U. Hopfer
Keyword(s):  
Sodium Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Serum Levels ◽  
Rat Colon ◽  
Sodium Absorption ◽  
Sodium Deficiency ◽  
Synthetic Glucocorticoids

The role of steroids in the regulation of colonic sodium transport was examined by infusing steroids into adrenalectomized (ADX) rats and evaluating the short-circuit current (ISC) in vitro. Amiloride-sensitive ISC was induced by aldosterone and corticosterone with half-maximal doses (ED50) of 2 and 260 micrograms X kg-1 X h-1), respectively. Synthetic glucocorticoids such as methylprednisolone (33 mg/kg) and dexamethasone (ED50 = 30 micrograms X kg-1 X h-1) were also effective. Supramaximal doses of aldosterone (7.5 times ED50) for 24 h increased the total ISC (7-fold), the amiloride-sensitive ISC (366-fold), and the conductance (2-fold), as well as the potassium-stimulated phosphatase activity (2-fold) (reported previously). Compared with aldosterone, supramaximal doses of dexamethasone (4 times ED50) produced greater increases in the total ISC (15-fold) and the amiloride-sensitive ISC (674-fold). In contrast to aldosterone, dexamethasone also increased the amiloride-insensitive ISC (3-fold). Glucocorticoid action was not mediated by insulin since the ISC from diabetic ADX rats was increased by dexamethasone to a similar extent (11-fold) as in nondiabetic rats. Estradiol, progesterone, and testosterone did not stimulate the colonic ISC of ADX rats. The ED50 values of corticosterone and aldosterone, measured in terms of amiloride-sensitive sodium transport, produced serum levels that were slightly above those of unstressed, adrenal-intact animals and thus must be considered physiological. It is concluded that at physiological levels both steroids may mediate amiloride-sensitive sodium transport in the rat colon. However, as judged from changes in serum steroid levels, aldosterone is the physiological regulator of elevated sodium absorption in sodium deficiency.

Alterations of the VIP-stimulated cAMP pathway in rat distal colon after abdominal irradiation

2002 ◽  
Vol 282 (5) ◽  
pp. G835-G843 ◽  
Author(s):  
E. Morel ◽  
I. Dublineau ◽  
F. Lebrun ◽  
N. M. Griffiths
Keyword(s):  
Short Circuit ◽  
Major Change ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Cell Number ◽  
Rat Colon ◽  
Camp Accumulation ◽  
Ussing Chambers ◽  
Abdominal Irradiation ◽  
Vip Receptor

Ionizing radiation induces hyporesponsiveness of rat colonic mucosa to vasoactive intestinal peptide (VIP). Possible mechanisms responsible for this hyporesponsiveness of the cAMP communication pathway in rat colon were investigated. VIP- and forskolin-stimulated short-circuit current ( I sc) responses were studied after a 10-Gy abdominal irradiation in Ussing chambers as well as in single, isolated crypts. Adenylyl cyclase (AC) activity and VIP receptor characteristics were determined in mucosal membrane preparations. In addition, alterations in crypt morphology were studied. Impaired secretory responses to VIP and forskolin were observed 4 days after irradiation (decrease of 80%). cAMP analog-stimulated I scresponses were unchanged. In isolated crypts, VIP- and forskolin-stimulated cAMP accumulation was markedly reduced by 80 and 50%, respectively. VIP-stimulated AC activity and VIP receptor number were decreased in membrane preparations. No major change of cellularity was associated with these functional alterations. In conclusion, the decreased secretory responses to VIP of rat colon are associated with reduced cAMP accumulation, decreased AC activity, and diminution of VIP receptor numbers without a marked decrease of crypt cell number.

Galanin-induced alteration of electrolyte transport in the rat intestine

1992 ◽  
Vol 263 (4) ◽  
pp. G502-G507
Author(s):  
T. Kiyohara ◽  
M. Okuno ◽  
H. Ishikawa ◽  
T. Nakanishi ◽  
Y. Shinomura ◽  
...  
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Electrical Field Stimulation ◽  
Distal Colon ◽  
Rat Colon ◽  
Chloride Absorption ◽  
Neural Transmission ◽  
36Cl Fluxes ◽  
Intestinal Ion Transport

Effects of rat and porcine galanin on rat intestinal ion transport were examined in vitro. In the rat distal colon, a sustained increase in short-circuit current (Isc) was produced by the serosal addition of rat galanin at a concentration as low as 10(-9) M, and a maximal increment was observed at 10(-7) M. Porcine galanin was approximately 100 times less potent than rat galanin. In the rat jejunum, rat galanin produced only a slight and transient decrease in basal Isc. The response to rat galanin was not influenced by atropine, hexamethonium, or amiloride, but was virtually abolished by tetrodotoxin or furosemide. Rat galanin did not significantly influence the increase in Isc elicited by electrical field stimulation in the rat colon and jejunum. Transmural unidirectional 22Na and 36Cl fluxes in the rat colonic mucosa were measured under short-circuited conditions, and rat galanin significantly decreased net sodium and net chloride absorption. These findings suggest that galanin acts as a secretory modulator in the rat colon via noncholinergic neural transmission.

Enhanced colonic Na+ absorption in cystic fibrosis mice versus normal mice

1997 ◽  
Vol 272 (2) ◽  
pp. G393-G400 ◽  
Author(s):  
B. R. Grubb ◽  
R. C. Boucher
Keyword(s):  
Cystic Fibrosis ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Proximal Colon ◽  
Na Channel ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
Constant Dose ◽  
Cf Transmembrane Conductance Regulator

Because there are reports that electrogenic Na+ absorption is increased in colonic epithelia of cystic fibrosis (CF) subjects, we tested whether amiloride-sensitive Na+ absorption was increased in the colonic epithelia of CF mice compared with normal mice on high- or low-Na+ diets. When mice consumed a diet high in Na+, none of the colonic regions (distal colon, proximal colon, or cecum) from either group of mice exhibited an amiloride-sensitive short-circuit current (Isc). However, when mice were placed on a low-Na+ diet for 2 wk, all three intestinal regions from the CF mice exhibited a significant response to amiloride (P < or = 0.05). In contrast, normal mice on the low-Na+ diet exhibited an amiloride-sensitive Isc that was smaller and only significant in the cecum and distal colon. Measurement of plasma aldosterone levels revealed that the CF mice on the low-Na+ diet had significantly greater aldosterone levels than similarly treated controls [8,906 +/- 1,039 (n = 14) vs. 5,243 +/- 1,410 pg/ml (n = 14), respectively]. When mice were infused with a constant dose of aldosterone (1 microg x g(-1) x day(-1)) for 7 days, the distal colon of the CF mice still had a significantly greater amiloride-sensitive Isc than did the normal distal colon. If the presence of CF transmembrane conductance regulator (CFTR) down-regulates Na+ absorption in the colonic tissue from normal mice, our data suggest that at least some CFTR may be colocalized with the Na+ channel. Alternatively, other factors may be involved.

Determination of short-circuit current in the in vivo perfused rat colon

1984 ◽  
Vol 246 (2) ◽  
pp. G151-G158 ◽  
Author(s):  
H. Knauf ◽  
K. Haag ◽  
R. Lubcke ◽  
E. Berger ◽  
W. Gerok
Keyword(s):  
Specific Resistance ◽  
Short Circuit ◽  
Input Resistance ◽  
Short Circuit Current ◽  
Proximal Colon ◽  
Open Circuit ◽  
Rat Colon ◽  
Length Constant

Current pulses (I) were injected into the lumen of proximal colonic segments in vivo, and the corresponding voltage deflections (delta PD) superimposed on the transcolonic PD were recorded. From the exponential decay of delta PD along the colon axis, the electrical length constant (lambda) was determined. Based on cable analysis the input resistance (= delta PD x = 0/I) and lambda made it possible to calculate the specific resistance (Rm) of the colonic epithelium as 128 +/- 16 omega X cm2. As Rm proved to be an ohmic resistor, the extrapolation from open-circuit PD (8-12 mV, lumen negative) to zero PD was feasible and made the calculation of short-circuit current (= PD/Rm) equal to 70 +/- 16 microA/cm2. In the presence of amiloride short-circuit current decreased to about 50%, whereas with theophylline it increased by about 30%. Substitution of luminal Na+ with choline or Cl- with cyclamate was associated with a marked increase of Rm. The rheogenic component of net Na+ transport was estimated to be only 8%. Electroneutral Na+ absorption functionally coupled with Cl- absorption displayed the characteristic feature of ion transport in the rat proximal colon.

Steroids alter ion transport and absorptive capacity in proximal and distal colon

1985 ◽  
Vol 249 (1) ◽  
pp. G113-G119 ◽  
Author(s):  
J. H. Sellin ◽  
R. C. DeSoignie
Keyword(s):  
Ion Transport ◽  
Absorptive Capacity ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Proximal Colon ◽  
High Rate ◽  
Transport Parameters ◽  
In Vitro Effects

Steroids are potent absorbagogues, increasing Na and fluid absorption in a variety of epithelia. This study characterizes the in vitro effects of pharmacological doses of gluco- and mineralocorticoids on transport parameters of rabbit proximal and distal colon. Treatment with methylprednisolone (MP, 40 mg im for 2 days) and desoxycortone acetate (DOCA, 12.5 mg im for 3 days) resulted in a significant increase in short-circuit current (Isc) in distal colon, suggesting an increase in basal Na absorption. Amiloride (10(-4) M) caused a significantly negative Isc in MP-treated tissue, demonstrating a steroid-induced, amiloride-insensitive electrogenic ion transport in distal colon. The effect of two absorbagogues, impermeant anions (SO4-Ringer) and amphotericin, were compared in control and steroid-treated distal colon. In controls, both absorbagogues increased Isc. Impermeant anions caused a rise in Isc in both MP and DOCA tissues, suggesting that the high rate of basal Na absorption had not caused a saturation of the Na pump. The steroid-treated colons, however, did not consistently respond to amphotericin. Amiloride inhibited the entire Isc in MP-treated distal colon that had been exposed to amphotericin; this suggested that amphotericin had not exerted its characteristic effect on the apical membrane of steroid-treated colon. In proximal colon, steroids did not alter basal rates of transport; however, epinephrine-induced Na-Cl absorption was significantly greater in MP-treated vs control (P less than 0.005). Steroids increase the absorptive capacity of both proximal and distal colon for Na, while increasing basal Na absorption only in the distal colon.(ABSTRACT TRUNCATED AT 250 WORDS)

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