Regional differences in the response to platelet-activating factor in rabbit colon

1992 ◽  
Vol 82 (6) ◽  
pp. 673-680 ◽  
Author(s):  
S. P. L. Travis ◽  
D. P. Jewell
Keyword(s):  
Ion Transport ◽  
Regional Differences ◽  
Chloride Transport ◽  
Short Circuit ◽  
Platelet Activating Factor ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Chloride Secretion ◽  
Anion Secretion ◽  
Ussing Chambers

1. Platelet-activating factor is an inflammatory mediator related to eicosanoids which is known to stimulate anion secretion in the distal colon. Since there are regional differences in ion transport within the colon, the influence of platelet-activating factors on ion transport and epithelial permeability has been studied in rabbit caecum and distal colon mounted in Ussing chambers. 2. The effect of platelet-activating factor (1–50 nmol/l) on net electrogenic ion transport was to stimulate a biphasic increase in short-circuit current in the distal colon but not in the caecum. The platelet-activating factor-induced rise in short-circuit current was shown by ion replacement and pharmacological inhibitor studies to be consistent with chloride and bicarbonate secretion in the early phase, but with chloride secretion alone in the later phase. The effect on ion transport was specific and reversible and was enhanced by 0.25% BSA. 3. Colonic permeability, assessed by transmucosal resistance and mannitol flux, was increased by platelet-activating factor in both the distal colon and the caecum. This was consistent with an effect on platelet-activating factor on the paracellular pathway, because resistance decreased even when transcellular chloride transport was inhibited by frusemide or ion replacement. A specific platelet-activating factor antagonist (U66985) inhibited the effects of platelet-activating factor in both the distal colon and the caecum. 4. The results show that platelet-activating factor stimulates anion secretion only in the distal colon, but increases permeability in both the caecum and the distal colon.

Site of Action of Platelet-Activating Factor within the Mucosa of Rabbit Distal Colon

1995 ◽  
Vol 88 (1) ◽  
pp. 51-57 ◽  
Author(s):  
S. P. L. Travis ◽  
B. Crotty ◽  
D. P. Jewell
Keyword(s):  
Short Circuit ◽  
Late Phase ◽  
Platelet Activating Factor ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Receptor Expression ◽  
Transepithelial Resistance ◽  
Epithelial Cell Line ◽  
Anion Secretion ◽  
Ussing Chambers

1. To determine how platelet-activating factor stimulates colonic anion secretion and increases epithelial permeability, epithelial sheets of rabbit distal colon excluding the submucosal neural plexus were mounted in Ussing chambers. The influence of specific inhibitors and 50 nmol/l platelet-activating factor on short-circuit current and transepithelial resistance was then investigated. 2. Pretreatment with 1 μmol/l indomethacin or 1 μmol/l doxantrazole abolished the biphasic stimulation of the short-circuit current and decrease in transepithelial resistance induced by platelet-activating factor. Addition of 10 μmol/l mepyramine attenuated the early phase and completely inhibited the late phase. Pretreatment with 1 μmol/l ranitidine, 0.1 μmol/l tetrodotoxin, 0.1 μmol/l ritanserin or a 5-lipoxygenase inhibitor (1 μmol/l MK886) had no effect. 3. To assess the influence of platelet-activating factor on epithelial function isolated from lamina propria elements, monolayers were cultured from a human colonic epithelial cell line (T-84). 4. The short-circuit current across monolayers mounted in Ussing chambers stimulated by 10 μmol/l ionomycin could be inhibited by pretreatment with ouabain or frusemide, consistent with the capacity for chloride secretion. Addition of platelet-activating factor (up to 500 nmol/l) had no effect on short-circuit current or transepithelial resistance. Receptor expression was examined with [3H]platelet-activating factor in isolated T-84 and HT-29 cells and found to be absent. 5. The influence of physiological concentrations of platelet-activating factor on colonic epithelial anion secretion and increased permeability in rabbit distal colon is indirect and consistent with mediation by prostaglandins released from mucosal mast cells. Other mediators, including histamine acting through H1 but not H2 receptors, may have a role. 5-Lipoxygenase metabolites or 5-HT2 receptors appear not to be involved and, contrary to previous reports, the influence of platelet-activating factor on colonic epithelial function is independent of the submucosal neural plexus.

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.

Ion transport characteristics of the murine trachea and caecum

1992 ◽  
Vol 82 (6) ◽  
pp. 667-672 ◽  
Author(s):  
S. N. Smith ◽  
E. W. F. W. Alton ◽  
D. M. Geddes
Keyword(s):  
Cystic Fibrosis ◽  
Ion Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Chloride Secretion ◽  
Open Circuit ◽  
Potential Difference ◽  
Cystic Fibrosis Gene ◽  
Tissue Type ◽  
Ussing Chambers

1. The basic defect in cystic fibrosis relates to abnormalities of ion transport in affected tissues, such as the respiratory and gastrointestinal tracts. The identification of the cystic fibrosis gene has enabled studies on the production of a cystic fibrosis transgenic mouse to be undertaken. Knowledge of normal ion transport will be necessary for the validation of any such animal model. We have therefore characterized selected responses of the murine trachea and caecum mounted in ‘mini’ Ussing chambers under open-circuit conditions. 2. Basal values for the trachea were: potential difference, 1.1 mV (sem 0.2; n=18); equivalent short-circuit current, 20.4 μA/cm2 (3.6); conductance, 18.2 mS/cm2 (1.7). Corresponding values for the caecum were: potential difference, 0.7 mV (0.1; n=18); equivalent short-circuit current, 11.0 μA/cm2 (1.6); conductance, 14.5 mS/cm2 (1.4). 3. Amiloride (10 μmol/l) produced a significant (P < 0.001) fall in potential difference of 43.0% (5.7) in the trachea, but had no significant effect in the caecum. 4. Subsequently, one of three protocols was used to assess the capacity of either tissue for chloride secretion. Addition of a combination of forskolin (1 μmol/l) and zardaverine (10 μmol/l) produced rises in the potential difference of 873% (509) in the trachea and 399% (202) in the caecum. Both A23187 (10 μmol/l) and phorbol dibutyrate (10 nmol/l) increased tracheal potential difference by 350% (182) and 147% (47), respectively. Neither had a significant effect in the caecum. 5. Subsequent addition of bumetanide caused a fall in the stimulated potential difference of between 39.8% and 71.7%, depending on secretagogue and tissue type. 6. When a homozygous transgenic cystic fibrosis mouse becomes available, these responses should allow such an animal to be distinguished from normal or heterozygous mice.

Expression of the chloride channel ClC-2 in the murine small intestine epithelium

2000 ◽  
Vol 279 (6) ◽  
pp. C1787-C1794 ◽  
Author(s):  
Katalin Gyömörey ◽  
Herman Yeger ◽  
Cameron Ackerley ◽  
Elizabeth Garami ◽  
Christine E. Bear
Keyword(s):  
Small Intestine ◽  
Chloride Channel ◽  
Chloride Transport ◽  
Short Circuit ◽  
Chloride Ion ◽  
Short Circuit Current ◽  
Chloride Secretion ◽  
Ussing Chambers ◽  
Dependent Change ◽  
Knockout Animals

The chloride channel ClC-2 has been implicated in neonatal airway chloride secretion. To assess its role in secretion by the small intestine, we assessed its subcellular expression in ileal segments obtained from mice and studied the chloride transport properties of this tissue. Chloride secretion across the mucosa of murine ileal segments was assessed in Ussing chambers as negative short-circuit current ( Isc). If ClC-2 contributed to chloride secretion, we predicted on the basis of previous studies that negative Iscwould be stimulated by dilution of the mucosal bath and that this response would depend on chloride ion and would be blocked by the chloride channel blocker 5-nitro-2-(3-phenylpropylamino) benzoic acid but not by DIDS. In fact, mucosal hypotonicity did stimulate a chloride-dependent change in Iscthat exhibited pharmacological properties consistent with those of ClC-2. This secretory response is unlikely to be mediated by the cystic fibrosis transmembrane conductance regulator (CFTR) channel because it was also observed in CFTR knockout animals. Assessment of the native expression pattern of ClC-2 protein in the murine intestinal epithelium by confocal and electron microscopy showed that ClC-2 exhibits a novel distribution, a distribution pattern somewhat unexpected for a channel involved in chloride secretion. Immunolabeled ClC-2 was detected predominantly at the tight junction complex between adjacent intestinal epithelial cells.

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.

H2 receptors mediate cyclical chloride secretion in guinea pig distal colon

1990 ◽  
Vol 258 (6) ◽  
pp. G887-G893 ◽  
Author(s):  
Y. Z. Wang ◽  
H. J. Cooke
Keyword(s):  
Guinea Pig ◽  
Chloride Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Chloride Secretion ◽  
Chloride Ions ◽  
H2 Antagonist ◽  
H2 Receptors ◽  
Peak Increase

We tested the hypothesis that histamine mediates ion secretion in the guinea pig distal colon by stimulating H2 receptors on submucosal neurons. Serosal addition of histamine evoked a transient increase in short-circuit current (Isc) followed by recurrent cyclical increases in Isc. The transient phase of the response was examined previously and was not investigated in these studies. Histamine (1.5-2.5 x 10(-5) M) evoked a peak increase in Isc of 177 +/- 25 microA/cm2 at intervals of 5 min for 1-2 h. The duration of each recurrent cycle averaged 2.1 +/- 0.3 min. The H2 agonist dimaprit evoked recurrent cycles that had larger amplitudes than those caused by histamine. In the presence of histamine or dimaprit, the amplitude of the first cycle of the response was always less than subsequent cycles, regardless of the initial concentration. The cyclical responses to histamine, 2-methylhistamine, or dimaprit were unaltered by the H1 blocker pyrilamine, were reduced by the H2 antagonist cimetidine, and were abolished by the neuronal blocker tetrodotoxin. Blockade of prostaglandin formation with piroxicam did not prevent the recurrent cycles. The recurrent cycles were inhibited by the chloride transport blocker bumetanide and by removal of chloride ions. Our results demonstrate that histamine mediates prolonged cyclical chloride secretion in the guinea pig distal colon by activating H2 receptors on submucosal neurons involved in regulation of epithelial chloride transport.

Stimulation of chloride secretion by baicalein in isolated rat distal colon

2002 ◽  
Vol 282 (3) ◽  
pp. G508-G518 ◽  
Author(s):  
W. H. Ko ◽  
V. W. Y. Law ◽  
W. C. Y. Yip ◽  
G. G. L. Yue ◽  
C. W. Lau ◽  
...  
Keyword(s):  
Colonic Mucosa ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Chloride Secretion ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
Ussing Chambers ◽  
Rat Distal Colon ◽  
Cystic Fibrosis Transmembrane

The effect of baicalein on mucosal ion transport in the rat distal colon was investigated in Ussing chambers. Mucosal addition of baicalein (1–100 μM) elicited a concentration-dependent short-circuit current ( I sc) response. The increase in I sc was mainly due to Cl−secretion. The presence of mucosal indomethacin (10 μM) significantly reduced both the basal and subsequent baicalein-evoked I sc responses. The baicalein-induced I sc were inhibited by mucosal application of diphenylamine-2-carboxylic acid (100 μM) and glibenclamide (500 μM) and basolateral application of chromanol 293B (30 μM), a blocker of KvLQT1 channels and Ba2+ ions (5 mM). Treatment of the colonic mucosa with baicalein elicited a threefold increase in cAMP production. Pretreating the colonic mucosa with carbachol (100 μM, serosal) but not thapsigargin (1 μM, both sides) abolished the baicalein-induced I sc. Addition of baicalein subsequent to forskolin induced a further increase in I sc. These results indicate that the baicalein evoked Cl− secretion across rat colonic mucosa, possibly via a cAMP-dependent pathway. However, the action of baicalein cannot be solely explained by its cAMP-elevating effect. Baicalein may stimulate Cl− secretion via a cAMP-independent pathway or have a direct effect on cystic fibrosis transmembrane conductance regulator.

Inhibition of VIP-stimulated ion transport by a novel Y-receptor phenotype in rabbit distal colon

1993 ◽  
Vol 264 (5) ◽  
pp. G848-G854 ◽  
Author(s):  
G. H. Ballantyne ◽  
J. R. Goldenring ◽  
F. X. Fleming ◽  
S. Rush ◽  
J. S. Flint ◽  
...  
Keyword(s):  
Ion Transport ◽  
Colonic Mucosa ◽  
Peptide Yy ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Ussing Chambers ◽  
Potent Inhibition ◽  
Colonic Secretion ◽  
Receptor Phenotype

Neurocrine, endocrine, and paracrine regulators are critical to the control of colonic secretion. These studies have investigated the inhibition of vasoactive intestinal polypeptide (VIP)-stimulated ion transport by peptide YY (PYY) and other Y-class effectors in rabbit distal colonic mucosa mounted in Ussing chambers. PYY decreased basal short-circuit current (Isc) but did not significantly change either basal Na+ or Cl- flux. PYY inhibited VIP-stimulated increases in Isc by up to 86% and abolished VIP-induced Cl- secretion. PYY decreased VIP-generated increases in Isc by a tetrodotoxin-insensitive mechanism. PYY inhibited cholera toxin-stimulated as well as forskolin-stimulated increases in Isc but failed to alter stimulation by 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP). PYY decreased VIP-stimulated increases in tissue cAMP by 88% and forskolin-stimulated increases by 84%. PYY, neuropeptide Y (NPY), (Leu31,Pro34)-NPY, and pancreatic polypeptide (PP) all demonstrated potent inhibition of VIP-stimulated increases in Isc. PYY-(13-36) demonstrated little effect on VIP stimulation. Thus the rabbit distal colon possesses a novel Y-class receptor phenotype that demonstrates high affinity for all three PP-fold peptides, NPY, PYY, and PP.

Protease-activated receptor-2 stimulates intestinal epithelial chloride transport through activation of PLC and selective PKC isoforms

2009 ◽  
Vol 296 (6) ◽  
pp. G1258-G1266 ◽  
Author(s):  
Jacques Q. van der Merwe ◽  
France Moreau ◽  
Wallace K. MacNaughton
Keyword(s):  
Serine Proteases ◽  
Chloride Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Immunoblot Analysis ◽  
Chloride Secretion ◽  
Intestinal Epithelial ◽  
Ussing Chambers ◽  
Pkc Isoforms ◽  
Gf 109203X

Serine proteases play important physiological roles through their activity at G protein-coupled protease-activated receptors (PARs). We examined the roles that specific phospholipase (PL) C and protein kinase (PK) C (PKC) isoforms play in the regulation of PAR2-stimulated chloride secretion in intestinal epithelial cells. Confluent SCBN epithelial monolayers were grown on Snapwell supports and mounted in modified Ussing chambers. Short-circuit current ( Isc) responses to basolateral application of the selective PAR2 activating peptide, SLIGRL-NH2, were monitored as a measure of net electrogenic ion transport caused by PAR2 activation. SLIGRL-NH2 induced a transient Isc response that was significantly reduced by inhibitors of PLC (U73122), phosphoinositol-PLC (ET-18), phosphatidylcholine-PLC (D609), and phosphatidylinositol 3-kinase (PI3K; LY294002). Immunoblot analysis revealed the phosphorylation of both PLCβ and PLCγ following PAR2 activation. Pretreatment of the cells with inhibitors of PKC (GF 109203X), PKCα/βI (Gö6976), and PKCδ (rottlerin), but not PKCζ (selective pseudosubstrate inhibitor), also attenuated this response. Cellular fractionation and immunoblot analysis, as well as confocal immunocytochemistry, revealed increases of PKCβI, PKCδ, and PKCε, but not PKCα or PKCζ, in membrane fractions following PAR2 activation. Pretreatment of the cells with U73122, ET-18, or D609 inhibited PKC activation. Inhibition of PI3K activity only prevented PKCδ translocation. Immunoblots revealed that PAR2 activation induced phosphorylation of both cRaf and ERK1/2 via PKCδ. Inhibition of PKCβI and PI3K had only a partial effect on this response. We conclude that basolateral PAR2-induced chloride secretion involves activation of PKCβI and PKCδ via a PLC-dependent mechanism resulting in the stimulation of cRaf and ERK1/2 signaling.

The effect of [Arg8]vasopressin on electrogenic chloride secretion in cultured rat epididymal epithelia

1994 ◽  
Vol 267 (2) ◽  
pp. C607-C616 ◽  
Author(s):  
K. B. Lai ◽  
W. O. Fu ◽  
W. H. Ko ◽  
H. C. Chan ◽  
P. Y. Wong
Keyword(s):  
Regional Differences ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Chloride Secretion ◽  
Induced Response ◽  
Efferent Duct ◽  
Ussing Chambers ◽  
Cauda Epididymidis ◽  
Dose Dependent Increase ◽  
Dose Dependent

Primary cultured rat efferent ductal epithelia and cauda epididymal epithelial were mounted in Ussing chambers to study the effect of arginine vasopressin (AVP) on chloride secretion in the male excurrent duct. The regional differences in the signal transduction pathways involved were also investigated. In both the efferent duct and the cauda epididymidis, basolateral addition of AVP resulted in a dose-dependent increase in the short-circuit current (Isc), which was mediated via V1 receptor. Replacement of ambient Cl- with gluconate or pretreatment of a Cl- channel blocker, diphenylamine-2-carboxylate (apical, 1 mM), completely abolished the response, whereas addition of amiloride had no effect on the Isc. Pretreating the epithelia of the efferent duct with indomethacin (apical, 5 microM) or forskolin (basolateral, 1 microM), but not thapsigargin (apical, 1 microM) or trifluoperazine (apical, 20 microM), significantly inhibited the AVP response (P < 0.001). By comparison, pretreating the epithelia of the cauda epididymidis with any of the four agents significantly reduced the AVP-evoked response. These results suggested that the stimulation of chloride secretion by AVP in the efferent duct and the cauda epididymidis is mediated by prostaglandin synthesis and involves adenosine 3',5'-cyclic monophosphate (cAMP) as a second messenger. In the cauda epididymidis, calcium, in addition to cAMP, may play a role in mediating the AVP-induced response.

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