Components of electrogenic transport in unstimulated equine tracheal epithelium

1991 ◽  
Vol 260 (6) ◽  
pp. L510-L515 ◽  
Author(s):  
L. Joris ◽  
P. M. Quinton
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Inhibitory Effect ◽  
Open Circuit ◽  
Tracheal Mucosa ◽  
Electrogenic Transport ◽  
Ussing Chambers ◽  
Tissue Resistance ◽  
Na Substitution ◽  
Significant Underestimation

Basic components of unstimulated electrolyte transport across equine tracheal mucosa were characterized. After the tissue was mounted in Ussing chambers, both current and tissue resistance gradually increased for approximately 60 min before reaching stable values. Thereafter, under open-circuit conditions, the tissue had a resistance of 250 +/- 14 omega.cm2, generated a transepithelial potential difference of -34 +/- 1.7 (SE) mV (referenced to the serosal side) and an equivalent short-circuit current (Ieqsc) of -149 +/- 10.2 microA/cm2. Even though 10(-5) M amiloride reduced the current by approximately 65%, mucosal Na+ substitution with choline decreased the current significantly more (approximately 80%), indicating that part of the Na(+)-dependent current was amiloride insensitive. No current decrease occurred after serosal application of 10(-4) M bumetanide, which was expected to inhibit Na(+)-K(+)-2Cl(-)-mediated Cl- secretion, even though bilateral Cl- substitution with gluconate reduced Ieqsc by approximately 30 microA/cm2. Continuous short-circuit conditions caused a reversible fall in the short-circuit current that was inhibited by amiloride but not by Cl- depletion, suggesting that sustained short circuiting leads to a significant underestimation of the amiloride-sensitive Na+ transport. In the absence of Cl-, the response to amiloride was significantly smaller, which suggests that Cl- depletion also has an inhibitory effect on electrogenic, amiloride-sensitive Na+ absorption.

Ion transport in dog tracheal mucosa: interaction between calcium and prostaglandins

1984 ◽  
Vol 247 (3) ◽  
pp. C182-C187 ◽  
Author(s):  
F. J. Al-Bazzaz ◽  
V. P. Yadava
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Free Solution ◽  
Tetraacetic Acid ◽  
Tracheal Mucosa ◽  
Progressive Decline ◽  
Ussing Chambers ◽  
Tissue Resistance ◽  
36Cl Fluxes ◽  
Mannitol Flux

Prostaglandins E1 and F2 alpha (PGE1 and PGF2 alpha) stimulate short-circuit current (SCC), tissue conductance (G), and net Cl secretion by canine tracheal mucosa. To determine if these actions of prostaglandins require extracellular Ca we tested the effects of PGE1 and PGF2 alpha on tracheal mucosa mounted in Ussing chambers when one side of the preparation was exposed to 0.2 mM ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid in Krebs-Henseleit solution without Ca. Lack of Ca from the mucosal bath was associated with increased G, lowered potential difference (PD), and severalfold increase of 22Na and 36Cl fluxes in both directions. Addition of 1 microM of PGE1 or PGF2 alpha to the Ca-free mucosal bath raised PD by 6 mV and SCC by 15 microA X cm-2 but decreased G by 1.4 mS X cm-2. Unidirectional 22Na and 36Cl fluxes decreased by 32-49% (n = 7, P less than 0.05). These findings suggest that the increase in G, most likely of the paracellular pathway and brought about by the lack of mucosal Ca, was partially reversible by PGE1 and PGF2 alpha. In contrast, when tissues were exposed to Ca-free solution on their submucosal side, PGE1 or PGF2 alpha were not able to reverse the progressive decline in PD and tissue resistance (n = 8). [14C]mannitol flux increased when Ca was absent from the mucosal bath; then addition of 1 microM PGF2 alpha caused a 37% decline in flux (n = 5). In contrast, the increase in the flux of [14C]mannitol found when the submucosal bath lacked calcium was not reversed by 1 microM PGE1.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium secretion in canine tracheal mucosa

1985 ◽  
Vol 59 (4) ◽  
pp. 1191-1195 ◽  
Author(s):  
F. J. Al-Bazzaz ◽  
T. Jayaram
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Potential Difference ◽  
Secretory Process ◽  
Metabolic Inhibitor ◽  
Tracheal Mucosa ◽  
Transepithelial Potential ◽  
Transepithelial Potential Difference

Calcium (Ca) affects many cellular functions of the respiratory tract mucosa and might alter the viscoelastic properties of mucus. To evaluate Ca homeostasis in a respiratory epithelium we investigated transport of Ca by the canine tracheal mucosa. Mucosal tissues were mounted in Ussing-type chambers and bathed with Krebs-Henseleit solution at 37 degrees C. Unidirectional fluxes of 45Ca were determined in tissues that were matched by conductance and short-circuit current (SCC). Under short-circuit conditions there was a significant net Ca secretion of 1.82 +/- 0.36 neq . cm-2 . h-1 (mean +/- SE). Under open-circuit conditions, where the spontaneous transepithelial potential difference could attract Ca toward the lumen, net Ca secretion increased significantly to 4.40 +/- 1.14 compared with 1.54 +/- 1.17 neq . cm-2 . h-1 when the preparation was short-circuited. Addition of a metabolic inhibitor, 2,4-dinitrophenol (2 mM in the mucosal bath), decreased tissue conductance and SCC and slightly decreased the unidirectional movement of Ca from submucosa to lumen. Submucosal epinephrine (10 microM) significantly enhanced Ca secretion by 2.0 +/- 0.63 neq . cm-2 . h-1. Submucosal ouabain (0.1 mM) failed to inhibit Ca secretion. The data suggest that canine tracheal mucosa secretes Ca; this secretory process is augmented by epinephrine or by the presence of a transepithelial potential difference as found under in vivo conditions.

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.

Interaction between sodium and chloride transport in canine tracheal mucosa

1979 ◽  
Vol 46 (1) ◽  
pp. 111-119 ◽  
Author(s):  
F. J. Al-Bazzaz ◽  
Q. Al-Awqati
Keyword(s):  
Hormonal Regulation ◽  
Chloride Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Na Transport ◽  
Tracheal Mucosa ◽  
Electrically Conductive ◽  
Ussing Chambers ◽  
Cl Secretion ◽  
Cl Transport

Canine tracheal mucosae were dissected and mounted as flat sheets in Ussing chambers. Unidirectional isotope fluxes of 22Na and 36Cl were performed across paired mucosae from the same animal. The average spontaneous potential difference was 42 + 1.2 mV (mean +/- SE) lumen negative. The short-circuit current (SCC) 3.09 +/- 0.36 mueq/cm2.h was accounted for by a net Cl secretion of 2.46 +/- 0.26 mueq/cm2.h toward the mucosa and net Na absorption of 0.46 +/- 0.13 mueq/cm2.h toward submucosa. Removal of Cl depressed SCC but had no effect on unidirectional or net Na transport (n = 7). By contrast, removal of Na (n = 6) or the addition of ouabain (n = 7) abolished net Cl secretion and greatly reduced SCC. Theophylline (n = 6) added to the submucosal bath no significant effect on Na transport but stimulated SCC and Cl secretion, suggesting hormonal regulation of Cl transport. The results suggest that the active transport of Na and Cl in this epithelium occur by electrically conductive pathways, i.e., the transport is “electrogenic.” Further it appears that Na transport is independent of the presence of Cl but that Cl transport depends on some parameter of active Na transport.

Electrical activity and sodium transfer across in vitro pig placenta

1986 ◽  
Vol 250 (3) ◽  
pp. R474-R484 ◽  
Author(s):  
C. P. Sibley ◽  
B. S. Ward ◽  
J. D. Glazier ◽  
W. M. Moore ◽  
R. D. Boyd
Keyword(s):  
Electrical Activity ◽  
Adrenergic Receptors ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Ussing Chambers ◽  
Drug Concentrations ◽  
Voltage Clamping ◽  
Pig Placenta

Electrical activity generated by pieces of pig placenta, taken from anesthetized animals and mounted in Ussing chambers, has been investigated. Ten minutes after the start of voltage clamping, potential difference (PD; fetal side positive, open circuit), short circuit current (SCC), and resistance were 5.9 +/- 0.4 (SE) mV, 8.6 +/- 0.5 microA X cm-2, and 720 +/- 45 omega X cm2, respectively (n = 50). Ouabain (10(-4) M) added to the fetal side caused a maximum decline in PD and SCC from the time of addition of -3.7 +/- 0.98 mV and -3.9 +/- 1.4 microA X cm-2 (n = 6); epinephrine (10(-5) M) added to the fetal side caused increases of +1.0 +/- 0.2 mV and +4.0 +/- 1.4 microA X cm-2, respectively (n = 14). Drug concentrations for 50% maximum response for the effect of a series of adrenergic agonists on SCC were (in M) isoproterenol 1.2 +/- 0.05 X 10(-8), norepinephrine 6.1 +/- 0.3 X 10(-8), epinephrine 2.4 +/- 0.1 X 10(-7), and phenylephrine 4.7 +/- 0.2 X 10(-5), suggesting the involvement of fetally oriented beta-adrenergic receptors. Fetal epinephrine (10(-5) M) also stimulated net Na+ flux (Jnet) toward the fetal side to an extent equal to its effect on SCC. In control experiments Jnet was small but was inhibited by fetal side ouabain (10(-4) M) to produce a maternally directed Jnet, significantly different to the SCC. Replacement of Na+ by choline reduced SCC markedly but did not abolish it. In the absence of Na+, epinephrine had no effect on SCC. These results suggest that active Na+ transfer is not completely responsible for the control electrical activity of pig placenta. Epinephrine, however, modulates SCC entirely by stimulating net Na+ transfer toward the fetal side.

Effects of neuropeptide Y and substance P on antigen-induced ion secretion in rat jejunum

1996 ◽  
Vol 271 (6) ◽  
pp. G987-G992 ◽  
Author(s):  
D. M. McKay ◽  
M. C. Berin ◽  
J. D. Fondacaro ◽  
M. H. Perdue
Keyword(s):  
Substance P ◽  
Neuropeptide Y ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Inhibitory Effect ◽  
Secretory Response ◽  
Antigen Uptake ◽  
Effector Cells ◽  
Ussing Chambers ◽  
Intestinal Hypersensitivity

We previously described a model of intestinal hypersensitivity in which isolated gut segments from sensitized rats demonstrated a rapid epithelial secretory response to luminal antigen that was mediated by mucosal mast cells and capsaicin-sensitive nerves. In this study, we examined the ability of the inhibitory neuropeptide, neuropeptide Y (NPY), to diminish the antigen-induced secretory response. Rats were sensitized to egg albumin (EA), and 12-14 days later, jejunal tissue was excised and mounted in Ussing chambers. NPY inhibited the short-circuit current (Isc) increase and Cl- secretion evoked by addition of EA to the luminal side of the tissue; neural blockade with tetrodotoxin (TTX) had a similar inhibitory effect. In contrast, NPY was much less effective, and TTX was completely ineffective, on the response to serosal antigen. Additional experiments examined the cell target for NPY action. NPY and TTX almost abolished the Isc response to electrical transmural stimulation of enteric nerves, suggesting a possible neural site of action. In addition, NPY significantly reduced baseline Isc; this inhibition involved both TTX-dependent and TTX-independent components. Because nerves were previously shown to facilitate antigen uptake and substance P was implicated in the response to only luminal antigen, we postulated that NPY was inhibiting nerves that facilitate antigen transport from the lumen to effector cells in the lamina propria. We therefore examined the effect of exogenous substance P added after NPY inhibition. Substance P restored the luminal antigen-induced secretory response to pretreatment values. We conclude that the neuropeptides play a significant role in immunophysiology by acting at neural and epithelial sites in the intestinal mucosa.

Spatial map of salts and saccharides on dog tongue

1988 ◽  
Vol 255 (1) ◽  
pp. R117-R122
Author(s):  
J. L. Garvin ◽  
R. Robb ◽  
S. A. Simon
Keyword(s):  
Spatial Heterogeneity ◽  
Open Circuit Potential ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Chorda Tympani ◽  
Chorda Tympani Nerve ◽  
Lingual Epithelium ◽  
Ussing Chambers ◽  
Chloride Salts

Front and rear regions of dog tongue were tested for spatial heterogeneity with respect to monovalent chloride salts (NaCl, KCl, and NH4Cl) and sweet tastants (sucrose, D-glucose, and L-glucose) by placing them in Ussing chambers where the open-circuit potential, Voc, and short-circuit current, Isc, were measured. The responses of Voc and Isc to 0.5 M NaCl were greater in the front of the tongue than in the rear, whereas the responses of Voc and Isc to 0.5 M sucrose were greater in the rear of the tongue than in the front. These results are similar to those of published neurophysiological measurements from the chorda tympani nerve and thalamus. These data suggest that the spatial heterogeneities seen in higher taste centers are present in the isolated lingual epithelium where primary taste transduction events occur.

Cholinergic inhibition of electrogenic sodium absorption in the guinea pig distal colon

2003 ◽  
Vol 284 (4) ◽  
pp. G617-G628 ◽  
Author(s):  
Hisayoshi Hayashi ◽  
Tomoko Suzuki ◽  
Takeshi Yamamoto ◽  
Yuichi Suzuki
Keyword(s):  
Epithelial Transport ◽  
Short Circuit ◽  
Cholinergic Neurons ◽  
Short Circuit Current ◽  
Electrical Field Stimulation ◽  
Distal Colon ◽  
Receptor Activation ◽  
Inhibitory Effect ◽  
Sodium Absorption ◽  
Ussing Chambers

Submucosal cholinergic and noncholinergic neurons in intestines have been shown to be involved in regulating epithelial transport functions, particularly stimulating Cl−secretion. This study investigates the role of submucosal cholinergic neurons in regulating electrogenic Na+absorption in distal colon. Amiloride-sensitive short-circuit current ( Isc) and22Na+flux were measured in mucosal and mucosal-submucosal preparations mounted in Ussing chambers. In the mucosal preparation, carbachol (CCh) added to the serosal side inhibited amiloride-sensitive Iscand amiloride-sensitive22Na+absorption. The inhibitory effect of CCh was observed at ∼0.1 μM, and maximum inhibition of ∼70% was attained at ∼30 μM (IC50= ∼1 μM). CCh-induced inhibition of amiloride-sensitive Iscwas almost totally abolished by 10 μM atropine. Treatment of the tissue with ionomycin markedly reduced amiloride-sensitive Isc, but a subsequent addition of CCh further decreased it. Also, CCh still had an inhibitory effect, although significantly attenuated, after the tissue had been incubated with a low-Ca2+solution containing ionomycin and BAPTA-AM. Applying electrical field stimulation to submucosal neurons in the mucosal-submucosal preparation resulted in inhibition of amiloride-sensitive Isc, ∼33% of this inhibition being atropine sensitive. Physostigmine inhibited amiloride-sensitive Isc, this effect being abolished by atropine. In conclusion, submucosal cholinergic and noncholinergic neurons were involved in inhibiting electrogenic Na+absorption in colon. This inhibition by cholinergic neurons was mediated by muscarinic receptor activation.

Thyroxine and Na+ transport in toad: role in transition from poikilo- to homeothermy

1979 ◽  
Vol 236 (3) ◽  
pp. C117-C124 ◽  
Author(s):  
B. C. Rossier ◽  
M. Rossier ◽  
C. S. Lo
Keyword(s):  
Urinary Bladder ◽  
Atpase Activity ◽  
Short Circuit ◽  
Stage Iv ◽  
Short Circuit Current ◽  
Inhibitory Effect ◽  
Base Line ◽  
Na Transport ◽  
Tissue Resistance

The effects of thyroxine (T4) on Na+ transport, oxygen consumption (QO2), and Na+-K+-ATPase activity were studied in the urinary bladder and liver of the toad Bufo marinus. In the bladder, T4 in vitro (10(-8) to 10(-6) M) had no significant effect on these parameters during 15 h of incubation. When injected intraperitoneally (approximately 20 microgram/(kg body wt.day) for 6 days), T4 lowered base-line, short-circuit current by 62% (P less than 0.0025) and potential difference by 37% (P less than 0.001), increasing tissue resistance by 40% (P less than 0.02). T4 depressed QO2/DNA (-25%, P less than 0.05) with no significant effect on Na+-K+-ATPase activity. In liver, T4 increased the recovery per cell DNA of mitochondrial proteins by 32% (P less than 0.025), corresponding to an increased QO2 (stage IV) of isolated mitochondria per cell DNA (+54%, P less than 0.01). There was no significant effect on Na+-K+-ATPase activity. These results suggest that, unlike its function in the rat, T4 in the toad does not regulate cellular thermogenesis by inducing Na+-K+-ATPase. This major difference could account at least in part for the transition from poikilothermy to homeothermy. In addition, T4 has a distinct inhibitory effect on Na+ transport in the urinary bladder, which suggests an antagonism to the action of aldosterone.

Aldosterone modulates electrogenic Cl secretion in the colon of the hen (Gallus domesticus)

1991 ◽  
Vol 261 (6) ◽  
pp. R1533-R1541 ◽  
Author(s):  
W. Clauss ◽  
V. Dantzer ◽  
E. Skadhauge
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Na Channel ◽  
Na Transport ◽  
Electrogenic Transport ◽  
Ussing Chambers ◽  
Cl Secretion ◽  
Cotransport System ◽  
Hormonal Stimulus

The regulation of Na and Cl transport in hen colon by mineralocorticoids was investigated with isolated epithelia in vitro by histological and electrophysiological techniques. The electrogenic transport of Na and Cl was measured in Ussing chambers by the short-circuit current technique and was identified by the specific inhibitors amiloride and bumetanide or by the secretagogue theophylline. Hens were maintained either on low (LS)- or on high-NaCl diets (HS), and the plasma aldosterone (PA) levels of these groups were measured with radioimmunoassay. A group of HS hens received injections of aldosterone at a 6-h schedule before experiments. A group of LS hens was resalinated, and experiments were carried out at a 24-h interval for up to 3 days after resalination. The LS diet stimulated PA levels ninefold, compared with HS hens. Na transport was modulated by the hormonal stimulus in a way that the apical Na entry switched from an electrogenic Na-amino acid-hexose cotransport system completely to an amiloride-sensitive Na channel. Electrogenic Cl secretion was induced by theophylline and was inhibited by bumetanide. NaCl deprivation, resalination or aldosterone injection modulated electrogenic Cl secretion in parallel between 7 (HS) and 14.4 mu eq.cm-2.h-1 (LS), with pronounced alteration in tissue conductance. These findings reveal a new action of aldosterone that, besides stimulating Na absorption, also directly or indirectly modulates Cl secretion.

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