Nitric oxide synthase stimulates prostaglandin synthesis and barrier function inC. parvum-infected porcine ileum

2004 ◽  
Vol 287 (3) ◽  
pp. G571-G581 ◽  
Author(s):  
Jody L. Gookin ◽  
Laurel L. Duckett ◽  
Martha U. Armstrong ◽  
Stephen H. Stauffer ◽  
Colleen P. Finnegan ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Barrier Function ◽  
Selective Inhibition ◽  
Prostaglandin Synthesis ◽  
Ileal Mucosa ◽  
Mucosal Permeability ◽  
Ussing Chambers ◽  
Nos Inhibitors ◽  
Culture Models ◽  
Nos Isoforms

Cell culture models implicate increased nitric oxide (NO) synthesis as a cause of mucosal hyperpermeability in intestinal epithelial infection. NO may also mediate a multitude of subepithelial events, including activation of cyclooxygenases. We examined whether NO promotes barrier function via prostaglandin synthesis using Cryptosporidium parvum-infected ileal epithelium in residence with an intact submucosa. Expression of NO synthase (NOS) isoforms was examined by real-time RT-PCR of ileal mucosa from control and C. parvum-infected piglets. The isoforms mediating and mechanism of NO action on barrier function were assessed by measuring transepithelial resistance (TER) and eicosanoid synthesis by ileal mucosa mounted in Ussing chambers in the presence of selective and nonselective NOS inhibitors and after rescue with exogenous prostaglandins. C. parvum infection results in induction of mucosal inducible NOS (iNOS), increased synthesis of NO and PGE2, and increased mucosal permeability. Nonselective inhibition of NOS ( NG-nitro-l-arginine methyl ester) inhibited prostaglandin synthesis, resulting in further increases in paracellular permeability. Baseline permeability was restored in the absence of NO by exogenous PGE2. Selective inhibition of iNOS [l- N6-(1-iminoethyl)-l-lysine] accounted for ∼50% of NOS-dependent PGE2synthesis and TER. Using an entire intestinal mucosa, we have demonstrated for the first time that NO serves as a proximal mediator of PGE2synthesis and barrier function in C. parvum infection. Expression of iNOS by infected mucosa was without detriment to overall barrier function and may serve to promote clearance of infected enterocytes.

Inducible nitric oxide synthase mediates early epithelial repair of porcine ileum

2002 ◽  
Vol 283 (1) ◽  
pp. G157-G168 ◽  
Author(s):  
Jody L. Gookin ◽  
J. Marc Rhoads ◽  
Robert A. Argenzio
Keyword(s):  
Nitric Oxide ◽  
Constitutive Expression ◽  
Mucosal Injury ◽  
Selective Inhibition ◽  
Acute Injury ◽  
Ileal Mucosa ◽  
Chronic Injury ◽  
Epithelial Repair ◽  
Ussing Chambers ◽  
Nos Inhibitors

Reports conflict regarding the effect of nitric oxide (NO) on intestinal epithelium. In chronic injury, NO appears detrimental by combining with reactive oxygen to form potent-free radicals. In contrast, inhibition of NO synthesis after acute injury exacerbates damage and inflammation. Recent studies have disclosed constitutive expression of inducible NO synthase (iNOS) by normal intestinal epithelia, yet little attention has been given to the role of iNOS in acute epithelial repair. We studied the local effects of iNOS on early epithelial repair of porcine ileal mucosa injured by deoxycholate within Ussing chambers. iNOS was constitutively expressed by the villous epithelium, and after deoxycholate injury, iNOS was expressed by injured and detaching enterocytes. Selective inhibition of iNOS abolished increases in NO synthesis and villous reepithelialization after injury. Exogenous l-arginine rescued baseline reepithelialization from NOS inhibitors but was only capable of stimulating additional repair in the presence of serum. These results demonstrate that iNOS-derived NO is a key mediator of early villous reepithelialization following acute mucosal injury.

Prostaglandin-mediated inhibition of Na+/H+ exchanger isoform 2 stimulates recovery of barrier function in ischemia-injured intestine

2006 ◽  
Vol 291 (5) ◽  
pp. G885-G894 ◽  
Author(s):  
Adam J. Moeser ◽  
Prashant K. Nighot ◽  
Kathleen A. Ryan ◽  
Jenna G. Wooten ◽  
Anthony T. Blikslager
Keyword(s):  
Barrier Function ◽  
Intestinal Ischemia ◽  
Short Circuit ◽  
Intestinal Barrier ◽  
Short Circuit Current ◽  
Selective Inhibition ◽  
Ileal Mucosa ◽  
Ussing Chambers ◽  
Nhe Isoforms

Prostaglandins stimulate repair of the ischemia-injured intestinal barrier in the porcine ileum through a mechanism involving cAMP-dependent Cl− secretion and inhibition of electroneutral Na+/H+ exchanger (NHE) activity. In the present study, we focused on the role of individual NHE isoforms in the recovery of barrier function. Ischemia-injured porcine ileal mucosa was mounted on Ussing chambers. Short-circuit current ( Isc), transepithelial electrical resistance (TER), and isotopic fluxes of 22Na were measured in response to PGE2 and selective inhibitors of epithelial NHE isoforms. Immunoassays were used to assess the expression of NHE isoforms. Forty-five minutes of intestinal ischemia resulted in a 45% reduction in TER ( P < 0.01). Near-complete restitution occurred within 60 min. Inhibition of NHE2 with HOE-694 (25 μM) added to the mucosal surface of the injured ileum stimulated significant elevations in TER, independent of changes in Isc and histological evidence of restitution. Pharmacological inhibition of NHE3 or NHE1 with mucosal S-3226 (20 μM) or serosal cariporide (25 μM), respectively, had no effect. Ischemia-injured tissues treated with mucosal S-3226 or HOE-694 exhibited equivalent reductions in mucosal-to-serosal fluxes of 22Na+ (by ∼35%) compared with nontreated ischemia-injured control tissues ( P < 0.05). Intestinal ischemia resulted in increased expression of the cytoplasmic NHE regulatory factor EBP50 in NHE2 but not in NHE3 immunoprecipitates. Selective inhibition of NHE2, and not NHE3, induces recovery of barrier function in the ischemia-injured intestine.

scholarly journals Nitric oxide synthase inhibitors negatively regulate respiration in isolated rodent cardiac and brain mitochondria

2020 ◽  
Vol 318 (2) ◽  
pp. H295-H300 ◽  
Author(s):  
Siva S. V. P. Sakamuri ◽  
Jared A. Sperling ◽  
Wesley R. Evans ◽  
Monica H. Dholakia ◽  
Aaron L. Albuck ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Mitochondrial Respiration ◽  
Isolated Heart ◽  
Protein S ◽  
Brain Mitochondria ◽  
Respiratory Parameters ◽  
Nos Inhibitors ◽  
Consumption Rates ◽  
Nos Isoforms

Nitric oxide (NO) is known to exert inhibitory control on mitochondrial respiration in the heart and brain. Evidence supports the presence of NO synthase (NOS) in the mitochondria (mtNOS) of cells; however, the functional role of mtNOS in the regulation of mitochondrial respiration is unclear. Our objective was to examine the effect of NOS inhibitors on mitochondrial respiration and protein S-nitrosylation. Freshly isolated cardiac and brain nonsynaptosomal mitochondria were incubated with selective inhibitors of neuronal (nNOS; ARL-17477, 1 µmol/L) or endothelial [eNOS; N5-(1-iminoethyl)-l-ornithine, NIO, 1 µmol/L] NOS isoforms. Mitochondrial respiratory parameters were calculated from the oxygen consumption rates measured using Agilent Seahorse XFe24 analyzer. Expression of NOS isoforms in the mitochondria was confirmed by immunoprecipitation and Western blot analysis. In addition, we determined the protein S-nitrosylation by biotin-switch method followed by immunoblotting. nNOS inhibitor decreased the state IIIu respiration in cardiac mitochondria and both state III and state IIIu respiration in brain mitochondria. In contrast, eNOS inhibitor had no effect on the respiration in the mitochondria from both heart and brain. Interestingly, NOS inhibitors reduced the levels of protein S-nitrosylation only in brain mitochondria, but nNOS and eNOS immunoreactivity was observed in the cardiac and brain mitochondrial lysates. Thus, the effects of NOS inhibitors on S-nitrosylation of mitochondrial proteins and mitochondrial respiration confirm the existence of functionally active NOS isoforms in the mitochondria. Notably, our study presents first evidence of the positive regulation of mitochondrial respiration by mitochondrial nNOS contrary to the current dogma representing the inhibitory role attributed to NOS isoforms. NEW & NOTEWORTHY Existence and the role of nitric oxide synthases in the mitochondria are controversial. We report for the first time that mitochondrial nNOS positively regulates respiration in isolated heart and brain mitochondria, thus challenging the existing dogma that NO is inhibitory to mitochondrial respiration. We have also demonstrated reduced protein S-nitrosylation by NOS inhibition in isolated mitochondria, supporting the presence of functional mitochondrial NOS.

Expression of nitric oxide synthase isoforms in normal ventilatory and limb muscles

1997 ◽  
Vol 83 (2) ◽  
pp. 348-353 ◽  
Author(s):  
Sabah N. A. Hussain ◽  
Qasim El-Dwairi ◽  
Mohammed N. Abdul-Hussain ◽  
Dalia Sakkal
Keyword(s):  
Nitric Oxide ◽  
Nitric Oxide Synthase ◽  
Fiber Type ◽  
Nos Inhibitors ◽  
Limb Muscles ◽  
Fiber Type Distribution ◽  
Neuronal Nos ◽  
Weak Expression ◽  
Oxide Synthase ◽  
Nos Isoforms

Hussain, Sabah N. A., Qasim El-Dwairi, Mohammed N. Abdul-Hussain, and Dalia Sakkal. Expression of nitric oxide synthase isoforms in normal ventilatory and limb muscles. J. Appl. Physiol. 83(2): 348–353, 1997.—Nitric oxide (NO), an important messenger molecule with widespread actions, is synthesized by NO synthases (NOS). In this study, we investigated the correlation between fiber type and NOS activity among ventilatory and limb muscles of various species. We also assessed the presence of the three NOS isoforms in normal skeletal muscles and how various NOS inhibitors influence muscle NOS activity. NOS activity was detected in various muscles; however, NOS activity in rabbits and rats varied significantly among different muscles. Immunoblotting of muscle samples indicated the presence of both the neuronal NOS and the endothelial NOS isoforms but not the cytokine-inducible NOS isoform. However, these isoforms were expressed to different degrees in various muscles. Although the neuronal NOS isoform was detectable in the canine diaphragm, very weak expression was detected in rabbit, rat, and mouse diaphragms. The endothelial NOS isoform was detected in the rat and mouse diaphragms but not in the canine and rabbit diaphragms. We also found that N G-nitro-l-arginine methyl ester, 7-nitroindazole, and S-methylisothiourea were stronger inhibitors of muscle NOS activity than was aminoguanidine. These results indicate the presence of different degrees of constitutive NOS expression in normal ventilatory and limb muscles of various species. Our data also indicate that muscle NOS activity is not determined by fiber type distribution but by other not yet identified factors. The functional significance of this expression remains to be assessed.

Fire Ant Venom Alkaloid, Isosolenopsin A, a Potent and Selective Inhibitor of Neuronal Nitric Oxide Synthase

2003 ◽  
Vol 22 (2) ◽  
pp. 81-86 ◽  
Author(s):  
G. B. Yi ◽  
D. Mc Clendon ◽  
D. Desaiah ◽  
J. Goddard ◽  
A. Lister ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Nitric Oxide Synthase ◽  
Inhibitory Activity ◽  
Systemic Toxicity ◽  
Fire Ant ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Nos Inhibitors ◽  
Oxide Synthase ◽  
Nos Isoforms

Massive, multiple fire ant, Solenopsis invicta, stings are often treated aggressively, particularly in the elderly, despite limited evidence of systemic toxicity due to the venom. Over 95% of the S. invicta venom is composed of piperidine alkaloid components, whose toxicity, if any, is unknown. To assess a possible pharmacological basis for systemic toxicity, an alkaloid-rich, protein-free methanol extract of the venom from whole ants was assayed for inhibitory activity on the following nitric oxide synthase (NOS) isoforms, rat cerebellar neuronal (n NOS), bovine recombinant endothelial (e NOS), and murine recombinant immunologic (i NOS). Cytosolic NOS activity was determined by measuring the conversion of [3H]arginine to [3H]citrulline in vitro. Rat n NOS activity was inhibited significantly and in a concentration-dependent manner by the alkaloid-rich venom extract. For n NOS, enzyme activity was inhibited by approximately 50% with 0.33 ± 0.06 μgg of this venom extract, and over 95% inhibition of the three isoforms, n NOS, e NOS, and i NOS, was found with doses of 60 μg in 60-μl reaction mixture. These results indicate that the alkaloid components of S. invicta venom can produce potent inhibition of all three major NOS isoforms. Isosolenopsin A ( cis-2-methyl-6-undecylpiperidine), a naturally occurring fire ant piperidine alkaloid, was synthesized and tested for inhibitory activity against the three NOS isoforms. Enzyme activities for n NOS and e NOS were over 95% inhibited with 1000 μM of isosolenopsin A, whereas the activity of i NOS was inhibited by only about 20% at the same concentration. The IC50 for each of three NOS isoforms was approximately 18 ± 3.9 μM for n NOS, 156 ± 10 μM for e NOS, and >1000 μM for i NOS, respectively. Kinetic studies showed isosolenopsin A inhibition to be noncompetitive with L-arginine ( Ki = 19 ± 2 μM). The potency of isosolenopsin A as an inhibitor of n NOS compares favorably with the inhibitory potency of widely used n NOS inhibitors. Inhibition of NOS isoforms by isosolenopsin A and structurally similar compounds may have toxicological significance with respect to adverse reactions to fire ant stings.

Recovery of mucosal barrier function in ischemic porcine ileum and colon is stimulated by a novel agonist of the ClC-2 chloride channel, lubiprostone

2007 ◽  
Vol 292 (2) ◽  
pp. G647-G656 ◽  
Author(s):  
Adam J. Moeser ◽  
Prashant K. Nighot ◽  
Kory J. Engelke ◽  
Ryuji Ueno ◽  
Anthony T. Blikslager
Keyword(s):  
Tight Junctions ◽  
Barrier Function ◽  
Structural Changes ◽  
Ex Vivo ◽  
Short Circuit ◽  
Mucosal Barrier ◽  
Ileal Mucosa ◽  
Signaling Mechanism ◽  
Ussing Chambers ◽  
Mucosal Barrier Function

Previous studies utilizing an ex vivo porcine model of intestinal ischemic injury demonstrated that prostaglandin (PG)E2 stimulates repair of mucosal barrier function via a mechanism involving Cl− secretion and reductions in paracellular permeability. Further experiments revealed that the signaling mechanism for PGE2-induced mucosal recovery was mediated via type-2 Cl− channels (ClC-2). Therefore, the objective of the present study was to directly investigate the role of ClC-2 in mucosal repair by evaluating mucosal recovery in ischemia-injured intestinal mucosa treated with the selective ClC-2 agonist lubiprostone. Ischemia-injured porcine ileal mucosa was mounted in Ussing chambers, and short-circuit current ( Isc) and transepithelial electrical resistance (TER) were measured in response to lubiprostone. Application of 0.01–1 μM lubiprostone to ischemia-injured mucosa induced concentration-dependent increases in TER, with 1 μM lubiprostone stimulating a twofold increase in TER (ΔTER = 26 Ω·cm2; P < 0.01). However, lubiprostone (1 μM) stimulated higher elevations in TER despite lower Isc responses compared with the nonselective secretory agonist PGE2 (1 μM). Furthermore, lubiprostone significantly ( P < 0.05) reduced mucosal-to-serosal fluxes of 3H-labeled mannitol to levels comparable to those of normal control tissues and restored occludin localization to tight junctions. Activation of ClC-2 with the selective agonist lubiprostone stimulated elevations in TER and reductions in mannitol flux in ischemia-injured intestine associated with structural changes in tight junctions. Prostones such as lubiprostone may provide a selective and novel pharmacological mechanism of accelerating recovery of acutely injured intestine compared with the nonselective action of prostaglandins such as PGE2.

Neuronal nitric oxide synthase-derived hydrogen peroxide is a major endothelium-dependent relaxing factor

2008 ◽  
Vol 295 (6) ◽  
pp. H2503-H2511 ◽  
Author(s):  
L. S. A. Capettini ◽  
S. F. Cortes ◽  
M. A. Gomes ◽  
G. A. B. Silva ◽  
J. L. Pesquero ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Constitutive Expression ◽  
Selective Inhibition ◽  
No Production ◽  
Relaxing Factor ◽  
Antisense Knockdown ◽  
Nos Inhibitors ◽  
Mouse Aorta ◽  
Oxide Synthase ◽  
Endothelial Nitric Oxide

Endothelium-dependent vasorelaxation in large vessels is mainly attributed to Nω-nitro-l-arginine methyl ester (l-NAME)-sensitive endothelial nitric oxide (NO) synthase (eNOS)-derived NO production. Endothelium-derived hyperpolarizing factor (EDHF) is the component of endothelium-dependent relaxations that resists full blockade of NO synthases (NOS) and cyclooxygenases. H2O2 has been proposed as an EDHF in resistance vessels. In this work we propose that in mice aorta neuronal (n)NOS-derived H2O2 accounts for a large proportion of endothelium-dependent ACh-induced relaxation. In mice aorta rings, ACh-induced relaxation was inhibited by l-NAME and Nω-nitro-l-arginine (l-NNA), two nonselective inhibitors of NOS, and attenuated by selective inhibition of nNOS with l-ArgNO2-L-Dbu-NH2 2TFA (L-ArgNO2-L-Dbu) and 1-(2-trifluoromethylphehyl)imidazole (TRIM). The relaxation induced by ACh was associated with enhanced H2O2 production in endothelial cells that was prevented by the addition of l-NAME, l-NNA, L-ArgNO2-L-Dbu, TRIM, and removal of the endothelium. The addition of catalase, an enzyme that degrades H2O2, reduced ACh-dependent relaxation and abolished ACh-induced H2O2 production. RT-PCR experiments showed the presence of mRNA for eNOS and nNOS but not inducible NOS in mice aorta. The constitutive expression of nNOS was confirmed by Western blot analysis in endothelium-containing vessels but not in endothelium-denuded vessels. Immunohistochemistry data confirmed the localization of nNOS in the vascular endothelium. Antisense knockdown of nNOS decreased both ACh-dependent relaxation and ACh-induced H2O2 production. Antisense knockdown of eNOS decreased ACh-induced relaxation but not H2O2 production. Residual relaxation in eNOS knockdown mouse aorta was further inhibited by the selective inhibition of nNOS with L-ArgNO2-L-Dbu. In conclusion, these results show that nNOS is constitutively expressed in the endothelium of mouse aorta and that nNOS-derived H2O2 is a major endothelium-dependent relaxing factor. Hence, in the mouse aorta, the effects of nonselective NOS inhibitors cannot be solely ascribed to NO release and action without considering the coparticipation of H2O2 in mediating vasodilatation.

scholarly journals PG-mediated closure of paracellular pathway and not restitution is the primary determinant of barrier recovery in acutely injured porcine ileum

2003 ◽  
Vol 285 (5) ◽  
pp. G967-G979 ◽  
Author(s):  
Jody L. Gookin ◽  
Joseph A. Galanko ◽  
Anthony T. Blikslager ◽  
Robert A. Argenzio
Keyword(s):  
Epithelial Cells ◽  
Barrier Function ◽  
Intestinal Barrier ◽  
Acute Injury ◽  
Intestinal Barrier Function ◽  
Ileal Mucosa ◽  
Epithelial Barrier Function ◽  
Ussing Chambers ◽  
Relative Contribution ◽  
Primary Determinant

Small bowel epithelium is at the frontline of intestinal barrier function. Restitution is considered to be the major determinant of epithelial repair, because function recovers in parallel with restitution after acute injury. As such, studies of intact mucosa have largely been replaced by migration assays of cultured epithelia. These latter studies fail to account for the simultaneous roles played by villous contraction and paracellular permeability in recovery of barrier function. NSAIDs result in increased intestinal permeability and disease exacerbation in patients with inflammatory bowel disease (IBD). Thus we examined the reparative attributes of endogenous PGs after injury of ileal mucosa by deoxycholate (6 mM) in Ussing chambers. Recovery of transepithelial electrical resistance (TER) from 20-40 Ω·cm2 was abolished by indomethacin (Indo), whereas restitution of 40-100% of the villous surface was unaffected despite concurrent arrest of villous contraction. In the presence of PG, resident crypt and migrating epithelial cells were tightly apposed. In tissues treated with Indo, crypt epithelial cells had dilated intercellular spaces that were accentuated in the migrating epithelium. TER was fully rescued from the effects of Indo by osmotic-driven collapse of the paracellular space, and PG-mediated recovery was significantly impaired by blockade of Cl- secretion. These studies are the first to clearly distinguish the relative contribution of paracellular resistance vs. restitution to acute recovery of epithelial barrier function. Restitution was ineffective in the absence of PG-mediated paracellular space closure. Failure of PG-mediated repair mechanisms may underlie barrier failure resulting from NSAID use in patients with underlying enteropathy.

scholarly journals Human Nitric Oxide Synthase—Its Functions, Polymorphisms, and Inhibitors in the Context of Inflammation, Diabetes and Cardiovascular Diseases

2020 ◽  
Vol 22 (1) ◽  
pp. 56
Author(s):  
Magdalena Król ◽  
Marta Kepinska
Keyword(s):  
Nitric Oxide ◽  
Free Radicals ◽  
Nitric Oxide Synthase ◽  
Cell Damage ◽  
Intercellular Signaling ◽  
Nos Inhibitors ◽  
Genes Encoding ◽  
Oxide Synthase ◽  
Nos Isoforms

In various diseases, there is an increased production of the free radicals needed to carry out certain physiological processes but their excessive amounts can cause oxidative stress and cell damage. Enzymes play a major role in the transformations associated with free radicals. One of them is nitric oxide synthase (NOS), which catalyzes the formation of nitric oxide (NO). This enzyme exists in three forms (NOS1, NOS2, NOS3), each encoded by a different gene. The following work presents the most important information on the NOS isoforms and their role in the human body, including NO synthesis in various tissues and cells, intercellular signaling and activities supporting the immune system and regulating blood vessel functions. The role of NOS in pathological conditions such as obesity, diabetes and heart disease is considered. Attention is also paid to the influence of the polymorphisms of these genes, encoding particular isoforms, on the development of these pathologies and the role of NOS inhibitors in the treatment of patients.

Physiological concentrations of bile salts inhibit recovery of ischemic-injured porcine ileum

2004 ◽  
Vol 287 (2) ◽  
pp. G399-G407 ◽  
Author(s):  
Nigel B. Campbell ◽  
Craig G. Ruaux ◽  
Donnie E. Shifflett ◽  
Jöerg M. Steiner ◽  
David A. Williams ◽  
...  
Keyword(s):  
Barrier Function ◽  
Bile Salts ◽  
Deoxycholic Acid ◽  
Paracellular Permeability ◽  
Mucosal Barrier ◽  
Histological Evaluation ◽  
Ileal Mucosa ◽  
Ussing Chambers ◽  
Mucosal Barrier Function ◽  
Mannitol Flux

We have previously shown rapid in vitro recovery of barrier function in porcine ischemic-injured ileal mucosa, attributable principally to reductions in paracellular permeability. However, these experiments did not take into account the effects of luminal contents, such as bile salts. Therefore, the objective of this study was to evaluate the role of physiological concentrations of deoxycholic acid in recovery of mucosal barrier function. Porcine ileum was subjected to 45 min of ischemia, after which mucosa was mounted in Ussing chambers and exposed to varying concentrations of deoxycholic acid. The ischemic episode resulted in significant reductions in transepithelial electrical resistance (TER), which recovered to control levels of TER within 120 min, associated with significant reductions in mucosal-to-serosal 3H-labeled mannitol flux. However, treatment of ischemic-injured tissues with 10−5 M deoxycholic acid significantly inhibited recovery of TER with significant increases in mucosal-to-serosal 3H-labeled mannitol flux, whereas 10−6 M deoxycholic acid had no effect. Histological evaluation at 120 min revealed complete restitution regardless of treatment, indicating that the breakdown in barrier function was due to changes in paracellular permeability. Similar effects were noted with the application of 10−5 M taurodeoxycholic acid, and the effects of deoxycholic acid were reversed with application of the Ca2+-mobilizing agent thapsigargin. Deoxycholic acid at physiological concentrations significantly impairs recovery of epithelial barrier function by an effect on paracellular pathways, and these effects appear to be Ca2+ dependent.

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