Mechanism of leukotriene D4 stimulation of Cl- secretion in rat distal colon in vitro

1993 ◽  
Vol 265 (3) ◽  
pp. G467-G473 ◽  
Author(s):  
C. S. Hyun ◽  
H. J. Binder
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Potential Difference ◽  
Maximal Response ◽  
Leukotriene D4 ◽  
Cl Secretion ◽  
Serotonergic Receptors ◽  
Mediators Of Inflammation

Lipoxygenase metabolites of arachidonic acid have been implicated as mediators of inflammation in inflammatory bowel disease (IBD). To assess their role in regulation of electrolyte transport, we investigated the effect of leukotriene D4 (LTD4) on ion transport across isolated rat colonic mucosa under voltage-clamp conditions. Serosal addition of LTD4 caused a dose-dependent rapid and transient increase in both short-circuit current (Isc) and potential difference, with maximal response at 1 microM. Pretreatment of the tissue with a specific LTD4 receptor antagonist (SKF-104353) inhibited these LTD4 effects. The effect of LTD4 on Isc and potential difference was also abolished by the absence of Cl- from both bathing solutions or by the presence of a Na(+)-K(+)-2Cl- cotransport inhibitor (bumetanide). A cyclooxygenase inhibitor (piroxicam) completely prevented the LTD4-induced increase in Isc. In addition, the effect of LTD4 on Isc was inhibited by either 5-hydroxytryptamine2 or 5-hydroxytryptamine3 antagonists (ketanserin and ICS-205-930, respectively). These results are consistent with a model in which LTD4 initially stimulates the synthesis from lamina propria cells of cyclooxygenase metabolites that induce electrogenic Cl- secretion, most likely via serotonergic receptors.

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.

Role of calcium in chloride secretion mediated by cAMP pathway activation in rabbit distal colon mucosa

1993 ◽  
Vol 264 (2) ◽  
pp. G252-G260 ◽  
Author(s):  
V. Calderaro ◽  
E. Chiosi ◽  
R. Greco ◽  
A. M. Spina ◽  
A. Giovane ◽  
...  
Keyword(s):  
Short Circuit ◽  
Fold Increase ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Chloride Secretion ◽  
Free Medium ◽  
Cl Secretion ◽  
Pathway Activation ◽  
Flux Measurements ◽  
Pg E2

Effects of Ca2+ on adenosine 3',5'-cyclic monophosphate (cAMP)-mediated Cl- secretion were investigated in intact mucosa and isolated crypt cells of rabbit descending colon. Addition of 10 microM prostaglandin (PG)E2 or forskolin to tissues incubated in Ca(2+)-free medium increased the size of short-circuit current (Isc) and Cl- secretion as estimated by unidirectional 36Cl flux measurements (net flux = -2.31 +/- 0.24 vs. -1.22 +/- 0.10 mueq.h-1.cm-2, n = 4, P < 0.001). Addition of 10 microM PGE2 to tissues incubated in 1.2 mM Ca2+ Ringer induced a 7-fold increase in mean cAMP level, whereas it produced an 11-fold increase in tissues exposed to Ca(2+)-free medium. Membrane preparations from whole mucosa incubated in Ca(2+)-free medium displayed a cyclic nucleotide phosphodiesterase activity significantly lower than controls (18.76 +/- 0.54 vs. 31.20 +/- 0.39 pmol cAMP. mg protein-1.min-1, means +/- SE, n = 4, P < 0.001). Ca2+ removal also affected adenylate cyclase (AC) responsiveness to agonists; AC activity increased in controls by 54 and 226% after stimulation with 10 microM PGE2 and forskolin, respectively, but it increased more (77 and 325%, respectively) after incubation in Ca(2+)-free solutions.(ABSTRACT TRUNCATED AT 250 WORDS)

cAMP-dependent sulfate secretion by the rabbit distal colon: a comparison with electrogenic chloride secretion

1997 ◽  
Vol 273 (1) ◽  
pp. C148-C160 ◽  
Author(s):  
R. W. Freel ◽  
M. Hatch ◽  
N. D. Vaziri
Keyword(s):  
Short Circuit ◽  
Basolateral Membrane ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Chloride Secretion ◽  
Disulfonic Acid ◽  
Cl Secretion ◽  
Cyclic Monophosphate ◽  
Anion Conductance ◽  
Flux Measurements

The ability of a Cl-secreting epithelium to support net secretion of an anion other than a halide was investigated with 35SO4 flux measurements across the isolated, short-circuited rabbit distal colon. In most experiments, 36Cl fluxes were simultaneously measured to validate the secretory capacity of the tissues. Serosal addition of dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP, 0.5 mM) stimulated a sustained net secretion of SO4 (about -3.0 nmol.cm-2.h-1 from a 0.20 mM solution) via an increase in the serosal-to-mucosal unidirectional flux, whereas Ca ionophore A-23187 (1 microM, serosal) produced a more transient stimulation of SO4 and Cl secretion. Net adenosine 3',5'-cyclic monophosphate (cAMP)-dependent SO4 and Cl secretion were strongly voltage sensitive, principally through the potential dependence of the serosal-to-mucosal fluxes, indicating an electrogenic transport process. Symmetrical replacement of either Na, K, or Cl inhibited cAMP-dependent SO4 secretion, whereas HCO3-free buffers had no effect on SO4 secretion. Serosal bumetanide (50 microM) or furosemide (100 microM) reduced DBcAMP-stimulated SO4 and Cl secretion, whereas serosal 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid or 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (50 microM) blocked DBcAMP-induced SO4 secretion while enhancing net Cl secretion and short-circuit current. Mucosal 5-nitro-2-(3-phenylpropylamino)benzoic acid partially inhibited SO4 secretion and completely inhibited Cl secretion. It is concluded that secretagogue-stimulated SO4 secretion, like Cl secretion, may be an electrogenic process mediated by diffusive efflux through an apical anion conductance. Cellular accumulation of SO4 across the basolateral membrane appears to be achieved by a mechanism that is distinct from that employed by Cl.

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.

Transmural fluxes of 5-hydroxytryptamine in guinea pig ileum

1983 ◽  
Vol 244 (4) ◽  
pp. G421-G425 ◽  
Author(s):  
H. J. Cooke ◽  
M. Montakhab ◽  
P. R. Wade ◽  
J. D. Wood
Keyword(s):  
Guinea Pig ◽  
Ganglion Cells ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Linear Functions ◽  
Guinea Pig Ileum ◽  
Serotonergic Receptors ◽  
Flat Sheet ◽  
Muscularis Externa

Transmural movement of 5-hydroxytryptamine (5-HT) was studied in guinea pig small intestine in vitro in order to test the hypothesis that there is mucosal 5-HT barrier in this species. Segments of guinea pig ileum were mounted as flat sheets in flux chambers or were everted and perfused. Mucosal-to-serosal (Jm leads to s) and serosal-to-mucosal (Js leads to m) fluxes of 5-HT were measured in the absence of 5-HT gradients and under open- or short-circuited conditions. The results indicated that substantial transmural movement of 5-HT occurred in these preparations. Both Jm leads to s and Js leads to m were linear functions of the 5-HT concentration over a range of 1-30 microM and were not significantly different in the two directions. Addition of 2,4-dinitrophenol to both sides of the tissue reduced short-circuit current to zero and increased both tissue conductance and unidirectional 5-HT fluxes. These results suggested that the 5-HT fluxes across the guinea pig ileum occurred by passive mechanisms. Fluxes of 5-HT across preparations with the muscularis externa removed were not significantly different from fluxes across intact preparations. Mucosal-to-serosal 5-HT fluxes in everted perfused sacs were comparable with fluxes in the flat-sheet preparations. The data are not consistent with the hypothesis of a "tissue barrier" that functions to prevent 5-HT from reaching serotonergic receptors on enteric ganglion cells or enteroendocrine cells.

Brain natriuretic peptide stimulates K and Cl secretion across porcine distal colon epithelium

1991 ◽  
Vol 260 (4) ◽  
pp. C750-C755 ◽  
Author(s):  
T. R. Traynor ◽  
S. M. O'Grady
Keyword(s):  
Brain Natriuretic Peptide ◽  
Natriuretic Peptide ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Ringer Solution ◽  
Ussing Chambers ◽  
Cl Secretion ◽  
The Difference ◽  
Distal Colon Epithelium

Porcine distal colon epithelium was mounted in Ussing chambers and bathed with porcine Ringer solution. The serosal addition of brain natriuretic peptide (BNP; 50 nM) or atriopeptin III (AP-III; 500 nM) produced significant increases (50-75 microA/cm2) in short-circuit current (Isc). These increases in Isc were not inhibited by pretreatment with tetrodotoxin (TTX) or 5,8,11,14-eicosatetraynoic acid (ETYA). Analysis of concentration-response relationships revealed that BNP was 5.8-fold more potent than AP-III in stimulating the Isc. BNP and AP-III significantly increased the serosal-to-mucosal (S----M) Cl flux and reduced net Cl absorption by 38 and 41%, respectively. The BNP-stimulated S----M Cl flux was abolished when HCO3 was removed. In contrast, the vasoactive intestinal peptide (VIP)-stimulated S----M Cl flux was not affected by HCO3 replacement. In addition to their effects on Cl transport, BNP and AP-III increased net Rb secretion by 79 and 58%, respectively. BNP-stimulated Rb secretion was reduced by 76% after HCO3 replacement. These results indicate that natriuretic peptides stimulate K- and HCO3-dependent Cl secretion which is not present under basal conditions or after VIP stimulation. The difference in potency between BNP and AP-III suggests that ANP-B receptors may mediate their effects on ion transport in the porcine colon.

Ba2+ inhibition of electrogenic Cl- secretion in vitro frog and piglet gastric mucosa

1980 ◽  
Vol 239 (3) ◽  
pp. G151-G160 ◽  
Author(s):  
W. L. McLennan ◽  
T. E. Machen ◽  
T. Zeuthen
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Inhibitory Effect ◽  
Surface Charges ◽  
Inhibitory Effects ◽  
Cl Secretion ◽  
High K ◽  
In Vitro Investigation ◽  
Newborn Pigs

Gastric mucosae from frogs and newborn pigs were used for in vitro investigation of the effects of Ba2+ (10 microM to 7 mM) on transepithelial potential difference (PD), resistance and conductance (G), short-circuit current (Isc), H+ secretion, and transepithelial fluxes of 36Cl-. Ba2+ in the serosal, but not the mucosal, solution of both preparations caused PD, G, Isc, and Cl- secretion (JnetCl, Isc conditions) to decrease, while H+ secretion remained constant. Because the oxyntic cells were most likely the site of action for Ba2+, these cells must have the capacity to secrete Cl- in excess of H+ ions. The inhibitory effect of Ba2+ was not due to competition in the serosal membrane by Ba2+ for surface charges, Ca2+ sites, Na+ sites, or Cl- sites. When [K+] in both the mucosal and serosal solutions or in just the serosal solution ([K+]s) alone was increased to 10 mM, the inhibitory effects of low [Ba2+] were reduced; however, at higher [Ba2+], Isc was stimulated. At least part of the Ba2+ effect seems to be due to blockage of K+ channels in the serosal membrane of oxyntic cells. High [K+]s also caused decreased PD and Isc (but increased G) with no change in H+ secretion. It is proposed that during Isc conditions, JnetCl involves a neutral Na+-dependent accumulation of Cl- within oxyntic cells and a passive, conductive efflux fromthe cells into the mucosal solution. Ba2+ and high [K+] may alter this transport by depolarizing and, under certain conditions, hyperpolarizing intracellular voltage.

Water and electrolyte transport by rabbit esophagus

1975 ◽  
Vol 229 (2) ◽  
pp. 438-443 ◽  
Author(s):  
DW Powell ◽  
SM Morris ◽  
DD Boyd
Keyword(s):  
Sodium Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Electrolyte Transport ◽  
Potential Difference ◽  
Sodium Absorption ◽  
Bathing Solution ◽  
Electrical Potential Difference

The nature of the transmural electrical potential difference and the characteristics of water and electrolyte transport by rabbit esophagus were determined with in vivo and in vitro studies. The potential difference of the perfused esophagus in vivo was -28 +/- 3 mV (lumen negative). In vitro the potential difference was -17.9 +/- 0.6 mV, the short-circuit current 12.9 +/- 0.6 muA/cm2, and the resistance 1,466 +/- 43 ohm-cm2. Net mucosal-to-serosal sodium transport from Ringer solution in the short-circuited esophagus in vitro accounted for 77% of the simultaneously measured short-circuit current and net serosal-to-mucosal chloride transport for 14%. Studies with bicarbonate-free, chloride-free, and bicarbonate-chloride-free solutions suggested that the net serosal-to mucosal transport of these two anions accounts for the short-circuit current not due to sodium absorption. The potential difference and short-circuit current were saturating functions of bathing solution sodium concentration and were inhibited by serosal ouabain and by amiloride. Thus active mucosal-to-serosal sodium transport is the major determinant of the potential difference and short-circuit current in this epithelium.

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.

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