Amiloride-sensitive salt and fluid absorption in small intestine of sodium-depleted rats

1985 ◽  
Vol 248 (1) ◽  
pp. G133-G141 ◽  
Author(s):  
P. C. Will ◽  
R. N. Cortright ◽  
R. G. Groseclose ◽  
U. Hopfer
Keyword(s):  
Small Intestine ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Proximal Colon ◽  
Salt Transport ◽  
Fluid Absorption ◽  
Major Pathway

Secondary hyperaldosteronism produced by Na+ depletion was associated with increases in salt and fluid absorption in both the small intestine and the distal colon but not in the cecum and the proximal colon. Because these changes had not been documented for the small intestine, this study focused on the regulation of this tissue. Increased NaCl and water absorption was expressed in vitro by increases in short-circuit current and transepithelial potential and in vivo by increased fluid absorption and a decreased luminal content of Na+ and water. For example, the short-circuit current in the ileum of Na+-depleted rats was 2-fold that of adrenalectomized and 1.3-fold that of adrenal-intact control animals. The short-circuit current was inhibitable 24 +/- 14% by micromolar concentrations of amiloride in Na+-deficient animals compared with 1 +/- 3% in control animals. Similarly, ileal fluid absorption in vivo was 2.3-fold higher in Na+-deficient relative to control animals. The additional fluid absorption was sensitive to 50 microM amiloride, whereas amiloride had no effect in control animals. Furthermore, the Na+ content of the chyme from the ileum of Na+-deficient animals was about half that of controls. These results suggest that mineralocorticoids can induce the amiloride-sensitive Na+ transporter in the small intestine and that this type of epithelial salt transport can become a major pathway for salt retention by the small intestine.

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.

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)

Low-dose glucocorticoids maintain Na-H exchange in distal colon of adrenalectomized rats

1991 ◽  
Vol 261 (3) ◽  
pp. F545-F553 ◽  
Author(s):  
C. P. Bastl ◽  
L. Bressler ◽  
G. Schulman ◽  
M. Mendez ◽  
E. J. Cragoe
Keyword(s):  
Short Circuit ◽  
In Vitro Study ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Ion Flux ◽  
Rat Colon ◽  
Anion Secretion ◽  
Stimulation Of

With in vivo perfusion we demonstrated that physiological doses of glucocorticoids restore Na and Cl absorption in adrenalectomized rat colon. The absorption is spironolactone and amiloride resistant and is inhibited by the Na-H inhibitor, 5-(N-ethyl-N-isopropyl)amiloride (EIPA), suggesting that glucocorticoids modulate Na-H antiport. The present in vitro study examines pathways mediated by glucocorticoids in adrenalectomized rat distal colon and rectum. In vivo administration of 2.5 micrograms/100 g body wt dexamethasone did not alter serosal-to-mucosal flux or tissue electrical parameters but restored mucosal-to-serosal flux and net Na and Cl absorption within 2–3 h of administration to levels found in intact rat colon. Transport was not inhibited by 10(-5) M amiloride but was eliminated by 10(-5) M EIPA. After 26 h of dexamethasone, an amiloride-resistant short-circuit current was stimulated, accompanied by increased residual ion flux in rectum, but not distal colon, suggesting that a delayed or secondary effect of glucocorticoids is stimulation of electrogenic anion secretion. Thus adrenalectomy reduces net ion flux in distal colon by its effect on electroneutral mucosal-to-serosal NaCl flux. Small doses of glucocorticoids completely ameliorate this effect via stimulation of the Na-H antiport. Glucocorticoids maintain basal electroneutral NaCl absorption in distal rat 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.

Enzyme- and mineralocorticoid receptor-controlled electrogenic Na+ absorption in human rectum in vitro

1995 ◽  
Vol 269 (1) ◽  
pp. G42-G48 ◽  
Author(s):  
H. J. Epple ◽  
J. D. Schulzke ◽  
H. Schmitz ◽  
M. Fromm
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Hill Coefficient ◽  
Complete Control ◽  
Human Rectum ◽  
In The Beginning ◽  
Mineralocorticoid Activity

In vivo electrogenic Na+ absorption (JeNa) in the human rectum is controlled by acute variation of aldosterone in nanomolar concentration range. In this study we report both the induction of JeNa in human rectum epithelium by nanomolar aldosterone added in vitro and the enzymatic control of glucocorticoid action on JeNa. JeNa was measured as amiloride-sensitive short-circuit current 8 h after addition of the respective steroid. Aldosterone (10 nM) caused JeNa of 5.7 +/- 1.4 mumol.h-1.cm-2. Cortisol in the same concentration did not induce significant JeNa. Because cortisol is readily inactivated by 11 beta-hydroxysteroid dehydrogenase (11 beta-HSD), the true mineralocorticoid activity of cortisol was evaluated after inhibition of 11 beta-HSD by carbenoxolone. Carbenoxolone alone did not exhibit mineralocorticoid activity. If cortisol (10 nM) was given together with carbenoxolone (1 microM), the resulting JeNa (4.5 +/- 0.4 mumol.h-1.cm-2) was not significantly different from that after 10 nM aldosterone, indicating equal intrinsic mineralocorticoid activity of cortisol and aldosterone. The same mechanisms were found in rat late distal colon. Kinetic data of carbenoxolone at 10 nM cortisol resulted in a Michaelis constant of 0.3 microMs, maximal absorption of 8.4 mumol.h-1.cm-2, and a Hill coefficient of 1.8. The effects of carbenoxolone and glycyrrhetinic acid did not differ. We conclude that JeNa is under complete control of mineralocorticoid action. "Spontaneous" JeNa in the beginning of the in vitro period can be explained by elevated steroid levels before tissue removal.(ABSTRACT TRUNCATED AT 250 WORDS)

Gene ablation for PEPT1 in mice abolishes the effects of dipeptides on small intestinal fluid absorption, short-circuit current, and intracellular pH

2010 ◽  
Vol 299 (1) ◽  
pp. G265-G274 ◽  
Author(s):  
Mingmin Chen ◽  
Anurag Singh ◽  
Fang Xiao ◽  
Ulrike Dringenberg ◽  
Jian Wang ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Intracellular Ph ◽  
Fluid Transport ◽  
Apical Membrane ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Intestinal Fluid ◽  
Fluid Absorption

PEPT1 function in mouse intestine has not been assessed by means of electrophysiology and methods to assess its role in intracellular pH and fluid homeostasis. Therefore, the effects of the dipeptide glycilsarcosin (Gly-Sar) on jejunal fluid absorption and villous enterocyte intracellular pH (pHi) in vivo, as well as on enterocyte[14C]Gly-Sar uptake, short-circuit current ( Isc) response, and enterocyte pHi in vitro were determined in wild-type and PEPT1-deficient mice and in mice lacking PEPT1. Immunohistochemistry for PEPT1 failed to detect any protein in enterocyte apical membranes in Slc15a1−/− animals. Saturable Gly-Sar uptake in Slc15a1−/− everted sac preparations was no longer detectable. Similarly, Gly-Sar-induced jejunal Isc response in vitro was abolished. The dipeptide-induced increase in fluid absorption in vivo was also abolished in animals lacking PEPT1. Since PEPT1 acts as an acid loader in enterocytes, enterocyte pHi was measured in vivo by two-photon microscopy in SNARF-4-loaded villous enterocytes of exteriorized jejuni in anesthetized mice, as well as in BCECF-loaded enterocytes of microdissected jejunal villi. Gly-Sar-induced pHi decrease was no longer observed in the absence of PEPT1. A reversal of the proton gradient across the luminal membrane did not significantly diminish Gly-Sar-induced Isc response, whereas a depolarization of the apical membrane potential by high K+ or via Na+-K+-ATPase inhibition strongly diminished Gly-Sar-induced Isc responses. This study demonstrates for the first time that proton-coupled electrogenic dipeptide uptake in the native small intestine, mediated by PEPT1, relies on the negative apical membrane potential as the major driving force and contributes significantly to intestinal fluid transport.

Control of electrogenic Na+ absorption in rat late distal colon by nanomolar aldosterone added in vitro

1993 ◽  
Vol 264 (1) ◽  
pp. E68-E73 ◽  
Author(s):  
M. Fromm ◽  
J. D. Schulzke ◽  
U. Hegel
Keyword(s):  
Short Circuit ◽  
Ussing Chamber ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Proximal Colon ◽  
Hill Coefficient ◽  
Late Response ◽  
Maximal Velocity ◽  
Time Courses

It has been possible to obtain in a mammalian epithelium of dietetically and surgically untreated animals a dose response of in vitro-added aldosterone (Aldo, 10(-10) to 10(-5) M) on electrogenic Na+ absorption (JeNa). JeNa was measured in the Ussing chamber on stripped rat late distal colon 8 h after in vitro addition of Aldo. Submaximal effects were obtained at 3 nM Aldo; after a lag time of 2 h, short-circuit current (Isc) increased to a maximum of 234 +/- 15 microA/cm2 and dropped after 0.1 mM amiloride to -18 +/- 3 microA/cm2, resulting in JeNa of 9.4 +/- 0.6 mumol.h-1 x cm-1. Net Na+ tracer fluxes and Isc exhibited parallel time courses, so that electroneutral Na+ transport was not induced in late distal colon by acute Aldo. A plot of JeNa vs. Na conductance revealed an electromotive force (ENa) of 126 +/- 1 mV for all Aldo concentrations tested. Kinetic data were as follows: Michaelis constant 1.2 nM, maximal velocity (Vmax) 10.5 mumol.h-1 x cm-2, and Hill coefficient 2.1. In contrast to the large effect in late distal colon, 3 nM Aldo caused JeNa of < 1 mumol.h-1 x cm-2 in early distal colon, proximal colon, and cecum. Antimineralocorticoid sensitivity and ENa did not vary with Aldo concentration or time of the experiment, consistent with a unique mechanism during the early and late response up to 8 h, as well as at mineralocorticoid and glucocorticoid Aldo concentrations. Acute Aldo in a range of 0.1–10 nM fully controls JeNa between zero and Vmax in late distal colon.(ABSTRACT TRUNCATED AT 250 WORDS)

Sodium transport by lamb proximal colon measured during early postnatal development

1982 ◽  
Vol 98 (1) ◽  
pp. 155-159 ◽  
Author(s):  
M. W. Smith ◽  
P. S. James
Keyword(s):  
Postnatal Development ◽  
Sodium Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Proximal Colon ◽  
Early Postnatal Development ◽  
The Third ◽  
Electrolyte Absorption ◽  
Chloride Absorption

SUMMARYProximal colons taken from lambs up to 3 weeks after birth were shown to transport both sodium and chloride from lumen to blood when incubated in vitro.Sodium transport fell into three phases during postnatal development. The first covered the period from birth to 3 days of age when sodium transport was high and equal to that calculated from measurement of short-circuit current. The second was seen in 5- and 7-day-old lambs where the short-circuit current was low and the net transport of sodium was negligible. The third was seen in 2-3-week-old lambs where sodium transport was high, but the short-circuit current was low.Chloride absorption by colons taken from 1-day-old lambs appeared to be in exchange for an anion, possibly bicarbonate. Chloride absorption by colons taken from 3-week-old lambs appeared to be electrogenie or coupled directly to the transport of sodium.A possible explanation for the failure of electrolyte absorption by colons taken from 5- and 7-day-old lambs is discussed.

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.

Ion transport by neonatal rabbit distal colon

1986 ◽  
Vol 250 (6) ◽  
pp. G754-G759 ◽  
Author(s):  
G. D. Potter ◽  
S. M. Burlingame
Keyword(s):  
Small Intestine ◽  
Short Circuit ◽  
Ussing Chamber ◽  
Electrical Conductance ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Ion Fluxes ◽  
Adult Rabbit ◽  
Rabbit Colon ◽  
Edge Damage

The neonatal small intestine is characterized by electrical conductance and permeability to ions higher than in the corresponding adult intestine. To investigate whether this property of the neonate is limited to the small intestine, or extends to the colon, a modified Ussing chamber for determination of transmucosal potential difference (PD), short-circuit current (Isc), transepithelial conductance (Gt), and ion fluxes in the neonatal rabbit distal colon was constructed. After care to reduce edge damage, Gt for the neonatal colon was found to be 8.4 +/- 0.3 mS . cm2 and for adult colon in the same chamber, 7.4 +/- 0.5 (P greater than 0.05). Net Na and Cl fluxes under short-circuit conditions were similar to those obtained in adult colon. Unidirectional ion fluxes were also similar to those of the adult. Net Na flux (JNanet) was incompletely inhibited by 10(-4) M of amiloride. Response to replacement of Na, Cl, and HCO3-, respectively, in the bathing solutions was not different from that expected in adult rabbit colon. Thus differences between adult and neonatal rabbit colon were small, and the increased conductance and unidirectional ion fluxes characteristic of the neonatal small intestine were not evident in the neonatal rabbit distal colon.

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