Active transport and exchange diffusion of Cl across the isolated skin of Rana pipiens

1985 ◽  
Vol 249 (3) ◽  
pp. F424-F431 ◽  
Author(s):  
K. Drewnowska ◽  
T. U. Biber
Keyword(s):  
Rana Pipiens ◽  
Recent Observation ◽  
Short Circuit ◽  
Flux Ratio ◽  
Short Circuit Current ◽  
Na Transport ◽  
Exchange System ◽  
Exchange Diffusion ◽  
Cl Transport ◽  
Apical Side

Transepithelial Cl influx and efflux were measured in pairs of frog skin (Rana pipiens) matched according to short-circuit current, tissue conductance, and transepithelial potential (TEP). The skins were bathed symmetrically in NaCl Ringer and voltage clamped at TEP values ranging from -60 to +60 mV. At 0 TEP, Cl influx and net inward Cl movement (in neq X h-1 X cm-2) were, respectively, 961 +/- 116 and 463 +/- 68 in NaCl Ringer, 509 +/- 52 and 202 +/- 53 in amiloride-treated skins, 4,168 +/- 777 and 1,444 +/- 447 in theophylline-treated skins, and 587 +/- 38 and 97 +/- 44 in Na-free Ringer. A correlation was discovered between short-circuit current and Cl fluxes corresponding to a 2:6:1 relationship between changes in active Na transport and active Cl transport. Deviations from the predicted Cl flux ratio indicate the presence of exchange diffusion in the range of spontaneously occurring TEPs, in contrast to observations on R. temporaria and R. esculenta. The experiments indicate that a substantial portion of transepithelial Cl movement proceeds transcellularly 1) via active Cl transport that is Na dependent, amiloride sensitive, stimulated by theophylline, and apparently correlated with active Na transport, and 2) by means of exchange diffusion that not only occurs under short-circuit conditions but also at positive TEPs. It is possible to explain both the exchange diffusion and the properties of active Cl transport by a Cl-HCO3 exchange system at the apical side of the transporting cell that interacts with a Na-H exchange mechanism, a notion consistent with the recent observation of an amiloride-induced decrease in intracellular pH.

Chloride transport inhibition by piretanide and MK-196 in bullfrog corneal epithelium

1981 ◽  
Vol 240 (1) ◽  
pp. F25-F29
Author(s):  
O. A. Candia ◽  
H. F. Schoen ◽  
L. Low ◽  
S. M. Podos
Keyword(s):  
Corneal Epithelium ◽  
Electrical Resistance ◽  
Chloride Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Na Transport ◽  
Cl Transport ◽  
Apical Side ◽  
Diuretic Agents ◽  
Cl Permeability

Two new diuretic agents, piretanide and MK-196, inhibited short-circuit current (SCC) across the isolated frog corneal epithelium. The effect is explained as an inhibition of active Cl transport. A definite decrease in SCC and an increase in electrical resistance was observed with both diuretics in concentrations as low as 10(-6) M. Piretanide, at 10(-4) M, reduced the SCC by 90%, reduced th unidirectional forward Cl flux from 0.60 to 0.28 mueq x h-1 x cm-2, and increased the resistance by 60%. There was no effect on the Cl backflux. At 10(-4) M, MK-196 reduced the SCC by 83% and increased the resistance by 72%, from 1.68 to 2.91 k omega x cm2. Replacement of Cl by SO4 in the bathing solutions resulted in a larger increase in resistance, from 1.68 to 3.80 k omega x cm2. The diuretics had no effect on active Na transport across the corneal epithelium. After the permeability of the apical side was increased by amphotericin B, the drugs could not inhibit the Cl-originated SCC. These results suggest that piretanide and MK-196 selectively inhibit active Cl transport in the cornea by blocking Cl permeability of the apical side of the epithelial cells.

In vitro studies of sodium transport across the lower intestine of a desert parrot

1980 ◽  
Vol 239 (3) ◽  
pp. R285-R290
Author(s):  
E. Skadhauge ◽  
T. J. Dawson
Keyword(s):  
Short Circuit ◽  
Electrical Potential ◽  
Flux Ratio ◽  
Short Circuit Current ◽  
Electrical Potential Difference ◽  
Na Transport ◽  
Salt Loading ◽  
Ussing Chambers ◽  
Lower Intestine

The lower intestine (coprodeum and colon) of the Australian parrot, the galah, was mounted in Ussing chambers. Short-circuit current (SCC), electrical potential difference (PD), and unidirectional fluxes of Na and Cl were measured in birds that were fed mixed seeds or were NaCl loaded. The net Na transport of both coprodeum and colon was nearly equal to the SCC, and the flux ratio for Cl was unity. In birds which received mixed seeds, average coprodeal Na transport was 7.8 mu eq . cm-2 . h-1, and PD was 19 mV. The Km for Na was 5.7 meq/l. In colon, Na transport was reduced by 67% and PD by 70%. The ratio between unidirectional Na and Cl fluxes in the serosa-mucosa direction was 0.7. Salt loading suppressed coprodeal, but increased colonic Na transport. The coprodeal and colonic SCC and NA transport of birds receiving mixed seeds were inhibited by amiloride on the mucosal side. Colonic SCC of NaCl-loaded birds was only slightly reduced by amiloride (by 17%), but stimulated by amino acids (by 18%).

Regulation of electrogenic Na+ transport across leech skin

1995 ◽  
Vol 268 (3) ◽  
pp. R605-R613 ◽  
Author(s):  
W. M. Weber ◽  
U. Blank ◽  
W. Clauss
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Na Channel ◽  
Monovalent Cations ◽  
Serosal Side ◽  
Na Transport ◽  
Permeability Ratio ◽  
Cyclic Monophosphate ◽  
Apical Side ◽  
Stimulation Of

The dorsal integument of the medical leech Hirudo medicinalis exhibits a marked amiloride-sensitive Na+ absorption. With 20 mM Na+ in the apical solution, the transepithelial short-circuit current (Isc) was approximately 40% higher than with 115 mM Na+, whereas the transepithelial potential (VT) with 20 mM Na+ was -35.7 +/- 4.5 and -20.6 +/- 2.6 mV with 115 mM Na+. Amiloride (100 microM) inhibition at 20 mM apical Na+ was also significantly larger than with 115 mM Na+ in the solution. Benzamil (100 microM) showed additional inhibition after amiloride. Large transient overshooting currents occurred only when 115 mM Na+ was added after some minutes of Na(+)-free apical solution. Addition of adenosine 3',5'-cyclic monophosphate (cAMP) to the serosal side in the presence of 115 mM apical Na+ nearly doubled Isc. This cAMP effect was reduced to only 20% in the presence of 20 mM Na+. Guanosine 3',5'-cyclic monophosphate (cGMP) slightly increased Isc, whereas ATP showed biphasic potency. Removal of calcium from the apical side resulted in a large stimulation of amiloride-sensitive Isc only in the presence of 115 mM Na+. When currents were activated with cAMP, a deprivation of Ca2+ modestly reduced the amiloride-sensitive Isc. The Na+ channel of leech integument was found highly selective for Na+ over other monovalent cations. The permeability ratio for Na+ over K+ was approximately 30:1; the selectivity relationship for the investigated cations was Na+ > Li+ > NH4+ > K+ approximately Cs+ approximately Rb+.

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.

The concentration-dependence of CRF-like diuretic peptide: mechanisms of action.

1998 ◽  
Vol 201 (11) ◽  
pp. 1753-1762 ◽  
Author(s):  
T M Clark ◽  
T K Hayes ◽  
G M Holman ◽  
K W Beyenbach
Keyword(s):  
Short Circuit ◽  
Second Messenger ◽  
Short Circuit Current ◽  
Paracellular Pathway ◽  
Ionophore A23187 ◽  
Na Transport ◽  
Principal Mechanism ◽  
Cl Transport ◽  
Mediated Effects ◽  
Stimulation Of

The mechanism of action of synthetic CCRF-DP, the corticotropin-releasing factor (CRF)-related diuretic peptide of the salt marsh mosquito Culex salinarius, was investigated in isolated Malpighian tubules of the yellow fever mosquito Aedes aegypti. A low concentration of CCRF-DP (10(-9)mol l-1) caused a small but insignificant increase in transepithelial secretion of NaCl and fluid, but significantly reduced transepithelial voltage and resistance without a change in short-circuit current, pointing to the stimulation of passive Cl- transport through the paracellular pathway as the principal mechanism of a mild diuresis. Significant changes in voltage and resistance but not in short-circuit current were duplicated by the ionophore A23187 (0.4 micromol l-1), suggesting Ca2+ as a second messenger at 10(-9)mol l-1 CCRF-DP. A high concentration of CCRF-DP (10(-7)mol l-1) significantly increased transepithelial secretion of NaCl and fluid and significantly increased short-circuit current, pointing to the stimulation of active Na+ transport through the transcellular pathway as the mechanism of a strong diuresis. This effect was mimicked by dibutyryl-cAMP, suggesting cAMP as a second messenger at 10(-7)mol l-1 CCRF-DP. Dibutyryl-cGMP had no effects. These results suggest dose-dependent, receptor-mediated effects of CCRF-DP that target discrete transport pathways via discrete second messengers: low concentrations of CCRF-DP cause a mild diuresis, apparently via Ca2+-mediated effects on paracellular Cl- transport, and high concentrations cause a strong diuresis via cAMP-mediated effects on active transcellular Na+ transport in addition to the effects on the paracellular pathway.

Characterization of conductive pathways in guinea pig distal colon in vitro

1985 ◽  
Vol 248 (2) ◽  
pp. G176-G183 ◽  
Author(s):  
W. Clauss ◽  
J. Durr ◽  
G. Rechkemmer
Keyword(s):  
Guinea Pig ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Na Transport ◽  
Cl Transport ◽  
Intracellular Na Activity ◽  
In Vitro Investigation ◽  
The Individual

Isolated mucosal sheets of guinea pig distal colon were studied in vitro in Ussing-type chambers, using a computer-controlled voltage clamp. A conductance of 8–12 mS/cm2 and spontaneous variations of the potential difference (Vt, -4 to +6 mV) and the short-circuit current (Isc, -1.6 to +1.5 mu eq X cm-2 X h-1) were observed. With use of a green feed diet these variations could be entirely attributed to the rate of Na transport. Unidirectional Na and Cl fluxes were measured, and for Na, K, and Cl transport the individual conductances and directions were estimated from the changes in Vt and Isc, using the appropriate blockers amiloride, barium, and piretanide. The sum of the electrogenic Na, K, and Cl transport determines the spontaneous electrical behavior of this epithelium. Na transport was further characterized with transepithelial and transapical current-voltage relations. Apical Na entry occurred by diffusion, intracellular Na activity was 12 mM, and apical Na permeability was calculated as 0.02 cm/h. This study represents the first in vitro investigation of electrogenic transport in this epithelium and shows that it closely resembles transport mechanisms found in rabbit colon.

Na and Cl Transport across the Isolated Anterior Intestine of the Plaice Pleuronectes Platessa

1981 ◽  
Vol 90 (1) ◽  
pp. 123-142
Author(s):  
M. M. P. RAMOS ◽  
J. C. ELLORY
Keyword(s):  
Chloride Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Negative Potential ◽  
Loop Diuretics ◽  
Significant Part ◽  
Cl Transport ◽  
Anterior Intestine ◽  
Short Circuit Currents ◽  
Na Uptake

1. The tissue was found to have a serosa negative potential, and short-circuit currents equivalent to the net Cl transport. 2. A significant part of the Cl uptake was Na dependent and a similar fraction of the Na uptake was Cl dependent. 3. Short-circuit current and uptake of both ions were inhibited by loop diuretics and analogues. 4. I80 and P.D. were abolished by ouabain. 5. The observations are consistent with the idea of a coupled NaCl entry into the cell, using the energy inherent in the Na gradient; Na being pumped out of the cells by the Na pump and followed electrically by Cl−. Net chloride transport and the serosa negative potential would be a consequence of the permselective properties of the junctions allowing Na but not Cl to recycle back to the mucosal solution.

Suppression of gastric acid secretion by furosemide in isolated gastric mucosa of guinea pig

1980 ◽  
Vol 239 (6) ◽  
pp. G532-G535 ◽  
Author(s):  
A. Ayalon ◽  
A. Corcia ◽  
G. Klemperer ◽  
S. R. Caplan
Keyword(s):  
Guinea Pig ◽  
Acid Secretion ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Electrical Conductance ◽  
Short Circuit Current ◽  
Cl Transport ◽  
Consequent Reduction ◽  
Net Flux ◽  
Mucosal Side

The effect of furosemide on acid secretion and Cl- transport was studied in isolated fundic mucosa of the guinea pig. Furosemide (10(-3) M), applied to the serosal side produced an immediate effect on the short-circuit current (Isc), lowering it by 47 +/- 2%. Potential difference decreased by 29 +/- 3%, electrical conductance by 18 +/- 4%, acid secretion by 38 +/- 1%, and net flux of Cl- from serosal-to-mucosal side by 37%. Application of the drug to the mucosal side produced similar effects on acid secretion and on the electrical parameters. It is suggested that furosemide blocks the entrance of Cl-, by the Na+--Cl- cotransport mechanism, through the basolateral membrane of the secreting cell. The consequent reduction in electrogenic Cl- transport would cause Isc and acid secretion to decrease. A reduction of Cl- conductance of the apical membrane, upon mucosal application of the drug, would cause similar effects on acid secretion and Cl- transport.

THE EFFECT OF VALINOMYCIN ON THE TOAD BLADDER: ANTAGONISM TO VASOPRESSIN AND ALDOSTERONE

1969 ◽  
Vol 45 (2) ◽  
pp. 287-295 ◽  
Author(s):  
P. J. BENTLEY
Keyword(s):  
Macrolide Antibiotic ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Water Transfer ◽  
Toad Bladder ◽  
Na Transport ◽  
Bathing Medium ◽  
Sodium Transfer ◽  
Sites Of Action ◽  
Subsequent Addition

SUMMARY The macrolide antibiotic valinomycin decreased short-circuit current (SCC, Na transport) across the isolated bladder of the toad. This effect was not overcome by increasing the K+ levels in the bathing medium or by the action of amphotericin B. The effects of vasopressin on both sodium and water transfer across the toad bladder were inhibited by valinomycin and the latter inhibition is non-competitive. The action of theophylline in increasing water transfer across the bladder was also inhibited. Cyclic AMP also increased water and Na+ transfer across the bladder but its action was not reduced by the macrolide. These results suggest that valinomycin inhibits adenyl cyclase. Aldosterone increases sodium transport across the toad bladder and this action was abolished by previous incubation of the tissue with the macrolide. Once the steroid-induced effect had been established subsequent addition of valinomycin did not alter the sodium transfer. Valinomycin thus appears to have several sites of action on the toad bladder.

Role of alpha 1- and alpha 2-adrenergic receptors in Cl- transport across frog corneal epithelium

1988 ◽  
Vol 255 (6) ◽  
pp. C724-C730 ◽  
Author(s):  
T. C. Chu ◽  
O. A. Candia
Keyword(s):  
Adenylate Cyclase ◽  
Corneal Epithelium ◽  
Apical Membrane ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Negative Influence ◽  
Adenylate Cyclase System ◽  
Positive Effects ◽  
Cl Transport ◽  
Beta Agonists

Norepinephrine, 10(-6) M, reduced Cl- transport by 26% in 75% of isolated frog corneal epithelia. This inhibition was not previously reported. Since beta-adrenergic agonists are known to only stimulate Cl- transport, the action of specific alpha 1- and alpha 2-agonists on Cl- transport and electrical parameters was investigated. Phenylephrine, an alpha 1-agonist always stimulated the Cl(-)-dependent short-circuit current (Isc), but less than the beta-agonists. UK-14,304-18 (UK), a selective alpha 2-agonist, reduced both the Isc (by 31% at 10(-5) M) and the stroma-to-tear unidirectional Cl- flux. UK hyperpolarized the apical membrane potential difference and increased the transepithelial resistance and apical-to-basolateral resistance ratio. UK reduced forskolin-stimulated adenylate cyclase activity by 36%. The electrophysiological effects of UK are consistent with a reduction of the Cl- permeability at the apical membrane. Pretreatment with UK sensitized the tissue for a greater effect by forskolin. Results show that the frog corneal epithelium also possesses alpha 1- and alpha 2-receptors, the latter negatively coupled to the adenylate cyclase system. Cl- transport is thus regulated by an interaction between the positive effects of beta- and alpha 1-stimulation and the negative influence of alpha 2-stimulation.

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