Inhibition of the transepithelial potential difference and short circuit current in the isolated frog skin by alloxan

1992 ◽  
Vol 102 (1) ◽  
pp. 29-32
Author(s):  
Claudia Soto ◽  
Jose L. Reyes ◽  
Areli Ramirez ◽  
Fernando Paz ◽  
Cuauhtemoc Perez
Keyword(s):  
Frog Skin ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Potential Difference ◽  
Transepithelial Potential ◽  
Transepithelial Potential Difference

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.

scholarly journals Influence of Transepithelial Potential Difference on the Sodium Uptake at the Outer Surface of the Isolated Frog Skin

1973 ◽  
Vol 61 (5) ◽  
pp. 529-551 ◽  
Author(s):  
Thomas U. L. Biber ◽  
Molly L. Sanders
Keyword(s):  
Outer Surface ◽  
Frog Skin ◽  
Sodium Concentration ◽  
Progressive Increase ◽  
Open Circuit ◽  
Potential Difference ◽  
Toad Skin ◽  
Transepithelial Potential ◽  
Transepithelial Potential Difference ◽  
Charged Carrier

The unidirectional uptake of sodium across the outer surface of the isolated frog skin (J12Na) was measured in the presence of transepithelial potential difference (Δψ) ranging from +100 to -100 mV. With a sodium concentration of 115 mM in the bathing solutions J12Na increases significantly when the spontaneous Δψ is reduced to zero by short-circuiting the skin. With an Na concentration of 6 mM a progressive increase J12Na can be observed when Δψ is decreased in several steps from +100 to -100 mV (serosal side positive and negative, respectively). The observed change J12Na amounts to a fraction only of that predicted from the shift in Δψ. The results suggest that under open circuit conditions the potential step across the outside surface is at most one half of Δψ and that the resistance across the outside and inside barrier of the skin is ohmic. This is in agreement with measurements of intracellular potentials in the frog skin and with resistance measurements carried out in the toad skin. The data strongly support the view that the saturating component of Jψ proceeds via a charged carrier system. Exposure to negative values of Δψ of 50 mV or more for times of 24 min or more result in a marked reduction of J12Na which shows only partial or no reversibility.

STIMULATORY ACTION OF ANGIOTENSIN II ON WATER AND ELECTROLYTE TRANSPORT BY THE PROXIMAL COLON OF THE RAT

1980 ◽  
Vol 86 (1) ◽  
pp. 35-43 ◽  
Author(s):  
A. DIEZ DE LOS RIOS ◽  
M. LABAJOS ◽  
A. MANTECA ◽  
M. MORELL ◽  
A. SOUVIRON
Keyword(s):  
Hydraulic Conductivity ◽  
Osmotic Shock ◽  
Short Circuit ◽  
Proximal Colon ◽  
Potential Difference ◽  
Nacl Transport ◽  
Stimulatory Action ◽  
Bathing Medium ◽  
Transepithelial Potential ◽  
Transepithelial Potential Difference

In segments of isolated proximal colon from bilaterally adrenalectomized and nephrectomized rats 10−12 g angiotensin/ml added to the serosal medium stimulated fluid transfer and sodium transport whose increase was accompanied by a decrease in transepithelial potential difference and short circuit current. Transepithelial electrical resistance remained unchanged. Replacement of chloride by sulphate in the bathing medium blocked the response to angiotensin. This suggested that angiotensin stimulated a coupled NaCl transport. Administration of aldosterone also blocked the response to angiotensin, suggesting that a low concentration of endogenous aldosterone is partly responsible for the action of angiotensin. This would explain the necessity for some form of pretreatment such as bilateral adrenalectomy and nephrectomy. Hydraulic conductivity of proximal colon sacs was computed from the variation in the water flow from serosa to mucosa in response to an osmotic shock. A significant (P < 0·01) increase in the hydraulic conductivity of the proximal colon of bilaterally adrenalectomized and nephrectomized rats was found when 10−12 g angiotensin/ml was present in the serosal bathing medium. The observed decrease in the transepithelial potential difference has been related to an action of angiotensin on the paracellular shunt pathway.

Nitric oxide-mediated regulation of transepithelial sodium and chloride transport in murine nasal epithelium

1999 ◽  
Vol 276 (3) ◽  
pp. L466-L473 ◽  
Author(s):  
Heather L. Elmer ◽  
Kristine G. Brady ◽  
Mitchell L. Drumm ◽  
Thomas J. Kelley
Keyword(s):  
Nitric Oxide ◽  
Chloride Transport ◽  
Chloride Secretion ◽  
Inos Expression ◽  
Potential Difference ◽  
Nasal Epithelium ◽  
Sodium Absorption ◽  
No Production ◽  
Transepithelial Potential ◽  
Transepithelial Potential Difference

Transepithelial ion transport is regulated by a variety of cellular factors. In light of recent evidence that nitric oxide (NO) production is decreased in cystic fibrosis airways, we examined the role of NO in regulating sodium and chloride transport in murine nasal epithelium. Acute intervention with the inducible NO synthase (iNOS)-selective inhibitor S-methylisothiourea resulted in an increase of amiloride-sensitive sodium absorption observed as a hyperpolarization of nasal transepithelial potential difference. Inhibition of iNOS expression with dexamethasone also hyperpolarized transepithelial potential difference, but only a portion of this increase proved to be amiloride sensitive. Chloride secretion was significantly inhibited in C57BL/6J mice by the addition of both S-methylisothiourea and dexamethasone. Mice lacking iNOS expression [NOS2(−/−)] also had a decreased chloride-secretory response compared with control mice. These data suggest that constitutive NO production likely plays some role in the downregulation of sodium absorption and leads to an increase in transepithelial chloride secretion.

A primary cation transport by a V-type ATPase of low specificity

1996 ◽  
Vol 199 (6) ◽  
pp. 1327-1334 ◽  
Author(s):  
J Küppers ◽  
I Bunse
Keyword(s):  
Ion Transport ◽  
Proton Transport ◽  
Short Circuit ◽  
Membrane Conductance ◽  
Short Circuit Current ◽  
Potential Difference ◽  
Lepidopteran Larvae ◽  
The Family ◽  
K Transport

The enzyme involved in outward K+ transport in insect epithelia belongs to the family of V-ATPases. Evidence has been reported relating the generation of the K+ gradient to a primary electrogenic proton transport via a distinct electrophoretic nH+/K+ antiport. The subject of this paper is the transport of K+ at a thread hair sensillum of the cockroach in situ. We recorded changes in the voltage and resistance of the ion-transporting membrane and of shifts in pH caused by inhibition of energy metabolism and by putative inhibitors of a proton/cation exchanger. The results are supplemented by previous determinations of the K+ activities in the same preparation. 1. In cockroach hair sensilla, the ion transport generates a membrane voltage of 105 mV. We found that the transport rendered the positive output compartment alkaline with respect to the cytoplasm by 1.0 pH unit compared with the pH at equilibrium distribution, and we infer that proton transport cannot be the process that energizes the generation of the K+ gradient. 2. The ion transport created an electrochemical potential difference for protons, DeltaetaH, of approximately 4.5 kJ mol-1, while the potential difference for K+, DeltaetaK, amounted to approximately 11 kJ mol-1. Both potential differences are directed to the cytosol. It follows from DeltaetaK/DeltaetaH that an antiport would have to be electrophoretic to drive K+ by DeltaetaH and it should, therefore, contribute to the membrane conductance. Amiloride and harmaline did not significantly change the pH in the adjacent spaces and did not affect the voltage or the resistance of the transporting membrane. Previous determinations of the impedance have shown that the ATP-independent conductance of this membrane is small, supporting the conclusion that it lacks an electrophoretic antiport. From these results, we deduce that K+ transport in cockroach sensilla is not secondary to a proton transport and an electrochemical proton gradient. The phenomena observed match the performance of a primary, electrogenic, cation-translocating ATPase of the type deduced from analyses of the short-circuit current at the midgut epithelium of lepidopteran larvae. The validity of the H+ transport/antiport hypothesis is discussed.

Transepithelial transport kinetics and Na entry in frog skin: effects of novobiocin

1976 ◽  
Vol 231 (6) ◽  
pp. 1866-1874 ◽  
Author(s):  
LJ Cruz ◽  
TU Biber
Keyword(s):  
Kinetic Parameters ◽  
Frog Skin ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Close Correlation ◽  
Transport Kinetics ◽  
Transepithelial Transport ◽  
Linear Component ◽  
Na Transport ◽  
Transepithelial Na Transport

Na+ entry across the outer surface of frog skin and transepithelial Na transport were studied simultaneously at different [Na] in either the presence or absence of novobiocin by direct measurements of J12 (unidirectional uptake) and Io (short-circuit current). J12 consisted of two components: one linear, the other saturable. The kinetic parameters of the saturating components in controls were close to the kinetic parameters of overall transepithelial transport (Jm12 = 1.68+/-0.13 mleq cm-2h-1; Io =1.80+/-0.14 mueq cm-2h-1. K12 = 6.02+/-1.27 mM;Kio=6.12+/-1.33 mM). Novobiocin significantly augmented net transepithelial Na transport by increasing J13. J31 remained unaffected. A 1:1 relationship between the saturating component of J12 and Io was observed in both treated and untreated skins at all [Na] tested. (Jm12Iom, k12, and Kio were significantly larger in treated skins, but despite very drastic changes in transport rates, a close correlation between kinetic parameters of entry step and transepithelial transport was maintained. This suggests that the kinetics of transepithelial transport may simply reflect those of the rate-limiting step: the Na entry across the outer barrier of the skin. The results indicate that the linear component of J12 is not involved in transepithelial transport kinetics.

Effects of choline and other quaternary ammonium compounds on Na movements in frog skin

1963 ◽  
Vol 205 (5) ◽  
pp. 1063-1066 ◽  
Author(s):  
Robert I. Macey ◽  
Daniel C. Koblick
Keyword(s):  
Quaternary Ammonium ◽  
Frog Skin ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Quaternary Ammonium Compounds ◽  
Average Increase ◽  
Current Increase ◽  
Sodium Flux ◽  
Radioactive Sodium ◽  
Ammonium Compounds

Effects of choline on short-circuit current and radioactive sodium flux were measured in isolated frog skins. Replacement of control ions (K or Mg) by choline in the outside solution increased the short-circuit current and inward Na flux. When K was the control ion, the average increase in short-circuit current was 52%; with Mg, it was 36%. In both cases, the increase in inward Na flux accounted for about 75% of the short-circuit current increase, while passive choline movement possibly accounted for the remainder. Similar results were obtained using tetramethylammonium and tetraethylammonium in place of choline. One implication of these results is that studies in which choline is used as an inert substitute for Na must be interpreted with caution.

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