Active and passive chloride movements across isolated amphibian skin

1964 ◽  
Vol 207 (5) ◽  
pp. 1010-1014 ◽  
Author(s):  
José A. Zadunaisky ◽  
Felisa W. De Fisch
Keyword(s):  
Antidiuretic Hormone ◽  
Chloride Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Chloride Ions ◽  
Amphibian Skin ◽  
Chloride Flux ◽  
Bufo Arenarum ◽  
Sodium Loss ◽  
Toad Bufo

Several aspects of chloride passage through isolated amphibian skin were studied. The chloride transport performed by the skin of the frog Leptodactylus ocellatus or the passive chloride fluxes observed in the skin of the toad Bufo arenarum Hensel are not affected by antidiuretic hormone. The chloride transport produces a negative potential and a short-circuit current in sodium-free solutions, though the unidirectional fluxes of chloride are greatly reduced under these conditions. The short-circuit current due to the chloride transport is smaller than the net chloride flux. It was found that this disagreement could be ascribed to a loss of sodium toward the inside from the sodium pool of the skin. Antidiuretic hormone did not affect the chloride current, nor the sodium loss from the skin. The isolated skin of the toad Bufo arenarum Hensel does not transport chloride ions. Thus the active transport of chloride observed in isolated skins of the frog Leptodactylus ocellatus does not depend on environmental conditions, since both animals live in the same surroundings.

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.

Oxygen consumption and active transport of ions by isolated frog gastric mucosa

1963 ◽  
Vol 204 (5) ◽  
pp. 812-816 ◽  
Author(s):  
J. G. Forte ◽  
R. E. Davies
Keyword(s):  
Oxygen Consumption ◽  
Gastric Mucosa ◽  
Chloride Transport ◽  
Short Circuit ◽  
Membrane Conductance ◽  
Short Circuit Current ◽  
Chloride Ions ◽  
Total Oxygen ◽  
Ph Stat ◽  
Stat Method

Isolated bullfrog gastric mucosae were suspended between two glass chambers and bathed with physiological salt solutions equilibrated with 5% CO2 and 95% O2. The transmucosal potential difference, short-circuit current and membrane conductance were measured. Oxygen consumption was measured polarographically and the rate of acid secretion was determined by the pH stat method. Values for the ratio of hydrogen ions secreted to the total oxygen molecules consumed were calculated for 84 experiments and yielded a mean ratio of 1.86 ± 0.51 (sd) with none of the values above 3.5. The ratio of chloride ions transported (calculated as short-circuit current of chloride ions plus hydrochloric acid) to total oxygen consumed for 84 experiments was found to be above 4.0 in 40% of the cases measured (mean 3.80 ± 0.68). A simple redox-pump hypothesis, with molecular oxygen as the electron acceptor, and with one ion moved for each electron transmitted is ruled out as the only operating mechanism to account for active chloride transport by frog gastric mucosa.

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.

scholarly journals Further Observations on the Regulation of KCl ABSORPTION ACROSS LOCUST RECTUM

1985 ◽  
Vol 116 (1) ◽  
pp. 153-167
Author(s):  
J. W. HANRAHAN ◽  
J. E. PHILLIPS
Keyword(s):  
Chloride Transport ◽  
Short Circuit ◽  
Membrane Conductance ◽  
Short Circuit Current ◽  
Membrane Resistance ◽  
Open Circuit ◽  
High K ◽  
K Concentration ◽  
K Permeability

1. Electrophysiological and tracer flux techniques were used to studyregulation of KC1 reabsorption across locust recta. Physiologically high K+levels (100 mmolI−1) on the lumen side stimulated net 36Cl flux and reduced the theoretical energy cost of anion transport under open-circuit conductions. 2. The stimulation of short-circuit current (Ibc i.e. active C− absorption) by crude corpora cardiaca extracts (CC) was not dependent on exogenous Ca2+. Stimulations of Ibc were greatly enhanced in the presence of theophylline, indicating that the rate of synthesis of cAMP is increased by CC extracts. High CC levels lowered transepithelial resistance (Rt), suggesting that chloride transport stimulating hormone (CTSH) regulates both active Cl− absorption and counter-ion (K+) permeability. 3. High mucosal osmolarity or K+ concentration decreased Ibc and caused a disproportionately large increase in Rt, consistent with a decrease in theshunt (K+) conductance. Measurements of relative mucosal-to-serosal membrane resistance confirmed that high mucosal K+ levels reduced apical membrane conductance. Lowering mucosal pH to values observed in vivo atthe end of resorptive cycles also inhibited Ibc, apparently without affecting K+ permeability.

Further Observations on the Physiology of Salinity Adaptation in the Crab-Eating Frog (Rana Cancrivora)

1968 ◽  
Vol 49 (1) ◽  
pp. 185-193
Author(s):  
MALCOLM S. GORDON ◽  
VANCE A. TUCKER
Keyword(s):  
Sea Water ◽  
Short Circuit ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Ringer Solution ◽  
Osmotic Concentration ◽  
Green Toad ◽  
The Face ◽  
Solution Bathing ◽  
Toad Bufo

1. Total rates of urea loss from adult euryhaline crab-eating frogs (Rana cancrivora) adapted to various environmental salinities between fresh water and 80 % sea water increase as salinity increases above 40% sea water. Oxygen consumption is constant in rate in all salinities studied. 2. The presence of urea in the Ringer solution bathing isolated pieces of skin of frogs adapted to 60% sea water increases both the electrical potential and the inwardly directed short-circuit current across the skin. 3. In skeletal muscle cells addition of intracellular solutes maintains tissue hydration in the face of large increases in plasma osmotic concentration in high-salinity media. Changes in the intracellular urea and free amino acid concentrations are primarily responsible for increases in intracellular osmotic concentration. 4. Some implications of these observations are discussed and comparisons made with the euryhaline green toad, Bufo viridis.

Mechanisms of sodium and chloride transport across equine tracheal epithelium

1990 ◽  
Vol 259 (6) ◽  
pp. L459-L467 ◽  
Author(s):  
G. J. Tessier ◽  
T. R. Traynor ◽  
M. S. Kannan ◽  
S. M. O3'Grady
Keyword(s):  
Chloride Transport ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Short Circuit Current ◽  
Ringer Solution ◽  
Tracheal Epithelium ◽  
Ussing Chambers ◽  
Cl Secretion ◽  
Cotransport System ◽  
Ethanesulfonic Acid

Equine tracheal epithelium, stripped of serosal muscle, mounted in Ussing chambers, and bathed in plasmalike Ringer solution generates a serosa-positive transepithelial potential of 10–22 mV and a short-circuit current (Isc) of 70–200 microA/cm2. Mucosal amiloride (10 microM) causes a 40–60% decrease in Isc and inhibits the net transepithelial Na flux by 95%. Substitution of Cl with gluconate resulted in a 30% decrease in basal Isc. Bicarbonate substitution with 20 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid decreased the Isc by 21%. The Cl-dependent Isc was inhibited by serosal addition of 1 mM amiloride. Bicarbonate replacement or serosal amiloride (1 mM) inhibits the net Cl flux by 72 and 69%, respectively. Bicarbonate replacement significantly reduces the effects of serosal amiloride (1 mM) on Isc, indicating its effect is HCO3 dependent. Addition of 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP; 100 microM) causes a 40% increase in Isc. This effect is inhibited by subsequent addition of 10 microM serosal bumetanide. Bumetanide (10 microM) reduces net Cl secretion following stimulation with 8-BrcAMP (100 microM). Serosal addition of BaCl2 (1 mM) causes a reduction in Isc equal to that following Cl replacement in the presence or absence of 100 microM cAMP. These results suggest that 1) Na absorption depends on amiloride-inhibitable Na channels in the apical membrane, 2) Cl influx across the basolateral membrane occurs by both a Na-H/Cl-HCO3 parallel exchange mechanism under basal conditions and by a bumetanide-sensitive Na-(K?)-Cl cotransport system under cAMP-stimulated conditions, and 3) basal and cAMP-stimulated Cl secretion depends on Ba-sensitive K channels in the basolateral membrane.

Chymotrypsin, ileal chloride transport, and neurotransmitters

1984 ◽  
Vol 247 (3) ◽  
pp. G253-G260 ◽  
Author(s):  
K. A. Hubel
Keyword(s):  
Cell Function ◽  
Chloride Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Electrical Field Stimulation ◽  
Chloride Secretion ◽  
Target Cells ◽  
Flux Chamber ◽  
Rabbit Ileum ◽  
Electrical Field

Electrical field stimulation (EFS) depolarizes nerves and causes chloride secretion by mucosa of rabbit ileum mounted in a flux chamber. To test the hypothesis that the transmitter is a peptide, we determined whether the EFS response was prevented by the endopeptidase chymotrypsin (CT). Serosal, but not mucosal, addition of CT (200 micrograms/ml) reduced the short-circuit current (Isc) response to EFS by 90% or more. CT also reduced Cl absorption by decreasing the mucosal-to-serosal flux, but it did not affect net Na absorption. CT prevented the response to vasoactive intestinal polypeptides, but the response returned when CT activity was eliminated. The response to EFS did not return, however, implying that CT damaged cells that released transmitter or epithelial target cells. CT reduced the Isc response to serotonin by 69% and to A23187 by 10% and did not affect the theophylline response. We conclude that 1) the effects of CT on cell function limit its usefulness in identifying peptide neurotransmitters in epithelium, 2) CT irreversibly inhibits ion transport responses to EFS and to serotonin, and 3) CT reduces absorption of Cl probably by affecting a calcium pathway that modifies Cl transport.

Selective effects of bumetanide on chloride transport in bullfrog cornea

1978 ◽  
Vol 234 (4) ◽  
pp. F297-F301
Author(s):  
O. A. Candia ◽  
H. F. Schoen
Keyword(s):  
Electrical Resistance ◽  
Loop Diuretic ◽  
Chloride Transport ◽  
Short Circuit ◽  
Ussing Chamber ◽  
Short Circuit Current ◽  
Selective Inhibitor ◽  
O2 Consumption ◽  
Na Transport ◽  
Bathing Medium

Frog corneas were mounted in a modified Ussing chamber and short-circuit current (SCC) and unidirectional Cl fluxes were measured. Bumetanide, a loop diuretic, at concentrations as low as 10(-7) M, reduced the SCC 29%. At 10(-5) M, bumetanide reduced the SCC 96% and increased transcorneal electrical resistance 20-51%. The forward Cl flux declined from 0.71 +/- 0.04 to 0.20 +/- 0.03 mueq/h.cm2 (n, 7), while, in separate experiments, the backward Cl flux did not change significantly (from 0.22 +/- 0.03 to 0.23 +/- 0.04; n, 7). When corneas were mounted in Cl-free Ringer and the net Na transport was stimulated with amphotericin B, 10(-5) M bumetanide had no effect on the SCC. In separate experiments the effect of 10(-5) M bumetanide on the O2 consumption was measured in a stirrer bath assembly. Bumetanide decreased the O2 consumption from 352 +/- 14 to 297 +/- 19 microliter/h.cm2 (significantly different from sham-treated controls). This decrease was similar to that obtained with furosemide or when Cl was removed from the bathing medium. We infer from these results that bumetanide is a selective inhibitor of active Cl transport in the bullfrog cornea.

Action of adenosine on chloride active transport of isolated frog cornea

1979 ◽  
Vol 237 (2) ◽  
pp. F121-F127
Author(s):  
B. S. Spinowitz ◽  
J. A. Zadunaisky
Keyword(s):  
Rana Catesbeiana ◽  
Chloride Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Adenyl Cyclase ◽  
Naturally Occurring ◽  
Chloride Pump ◽  
Net Flux ◽  
The One ◽  
Sustained Increase

Addition of adenosine (10–7 to 10–4 M) to the tear side of isolated corneas (Rana catesbeiana) produced a rapid, sustained increase in short-circuit current, potential difference, and radioisotopic chloride net flux. The increased net chloride flux accounted for the increased short-circuit current. Adenosine, a known activator of adenyl cyclase in other tissues, exerted its effects on chloride transport through a receptor different from the one described for epinephrine and prostaglandins in the corneal epithelium. Propranolol inhibited the epinephrine response but not the adenosine effect. Dipolyphloretin phosphate inhibited prostaglandin responses but did not affect the adenosine stimulation of chloride transport. Adenine and/or ribose, parts of the adenosine molecule, had no stimulatory effect, but 5'-AMP had a partial effect.The activation of the chloride pump with DBcAMP blocked the response to adenosine. Adenosine interacted with the effects of theophylline. Adenosine, a naturally occurring molecule, stimulated chloride transport by activation of adenyl cyclase through a separate membrane receptor in the corneal eqithelium.

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