Ion transport across rumen and omasum epithelium

1971 ◽  
Vol 262 (842) ◽  
pp. 301-305 ◽  
Keyword(s):  
Active Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Chloride Ions ◽  
Rumen Epithelium ◽  
Sodium Flux ◽  
Sodium System ◽  
Chloride Pump ◽  
Net Flux ◽  
Cattle And Sheep

The interior of the rumen in cattle and sheep is normally maintained at a potential of about — 40 mV relative to the blood. This potential depends primarily on the occurrence of an active transport of sodium from rumen to blood, since the potential, short-circuit current and the net sodium flux are simultaneously abolished by anoxia, ouabain and removal of sodium from the bathing solutions. There is an appreciable net flux of potassium from blood to rumen. There is also a substantial active transport of chloride in the same direction as sodium and it can be reduced by treatment with acetazolamide without affecting the potential or the sodium system. Nevertheless, sodium transport is reduced by the removal of chloride ions. Omasum epithelium is similar to rumen epithelium. However, the chloride pump appears to work in both directions in this tissue. Short-circuited omasum epithelium can also transport magnesium from omasum to blood.

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.

Absorption of Fluid by the Midgut of Rhodnius

1981 ◽  
Vol 94 (1) ◽  
pp. 301-316 ◽  
Author(s):  
J. FARMER ◽  
S.H. P. MADDRELL ◽  
J. H. SPRING
Keyword(s):  
Cyclic Amp ◽  
Active Transport ◽  
Electrical Resistance ◽  
Fluid Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Chloride Ions ◽  
Potential Difference ◽  
Sodium Ions ◽  
Transport Fluid

1. Isolated midguts of 5th-instar Rhodnius prolixus will transport fluid from the lumen that is close to iso-osmotic with the luminal contents. 2. The transported fluid contains sodium and chloride ions as its major constituents. 3. Fluid transport can be attributed to active transport of sodium ions from the lumen. The haemolymph side of the epithelium, towards which transport is directed, is at a potential positive with respect to the lumen; this potential difference is greatly increased if the lumen contains only impermeant anions, and the rate of fluid transport is strongly dependent on the concentration of sodium ions in the luminal fluid. 4. The rate of fluid transport is increased approximately six times by treatment with 5-hydroxytryptamine (2×10−7M) or cyclic AMP (2x−3M). The transepithelial potential is increased by such treatment but the major effects are on the short-circuit current, which increases by about five times, and on the electrical resistance of the epithelium, which falls to about a quarter of its earlier value. Note:

Transport of sodium and chloride by the isolated rumen epithelium

1964 ◽  
Vol 206 (5) ◽  
pp. 1099-1105 ◽  
Author(s):  
Charles E. Stevens
Keyword(s):  
Sodium Chloride ◽  
Active Transport ◽  
Chloride Transport ◽  
Short Circuit ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Exchange Diffusion ◽  
Rumen Epithelium ◽  
Tissue Resistance ◽  
Affected Tissue

Transepithelial electrical potential, short-circuit current, and resistance measurements were made under different conditions of tissue collection and maintenance. The collection procedure greatly affected tissue resistance and, since the magnitude of the current was relatively independent of the procedure, potential was affected to about the same degree. The highest and least variable resistances were recorded when the tissue was removed from the anesthetized cow and the epithelium carefully dissected free. Short-circuit current and net ion flux decreased with time but the decrease was relatively linear and sufficiently slow to allow their comparison. Rumen epithelium of both species demonstrated active transport of Na and Cl in the direction of lumen to blood. Calculation of partial Na conductances indicated that part of the sodium was transported by exchange diffusion or a sodium chloride transport system.

scholarly journals The Origin of the Short-Circuit Current in the Isolated Skin of the South American Frog Leptodactylus ocellatus

1963 ◽  
Vol 47 (2) ◽  
pp. 393-402 ◽  
Author(s):  
José A. Zadunaisky ◽  
Oscar A. Candia ◽  
Dante J. Chiarandini
Keyword(s):  
Copper Ions ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Chloride Ions ◽  
Potential Difference ◽  
South American ◽  
The South ◽  
Net Flux ◽  
American Frog ◽  
Short Circuit Condition

In isolated skins of Leptodactylus ocellatus the short-circuit current is smaller than the sodium net flux and this difference disappears when the skins are bathed in solutions in which the chloride ions have been replaced by sulfate or methylsulfate ions. There is a net movement of chloride ions from outside to inside of the skins in the short-circuit condition with chloride Ringer's solutions bathing the skins. The addition of ouabain to the inside solution markedly reduced not only sodium net flux but also the chloride net influx found. Copper ions added to the outside solutions produced a rise in short-circuit current, as well as the known increase in potential difference. In sodium-free Ringer's (sodium replaced by choline) the orientation of the potential difference across the skins was reversed, the inside being negative instead of positive. The results are interpreted as direct or indirect indications of the presence of a net transfer of chloride ions from outside to inside of these frog skins.

scholarly journals Active Transport of Sodium by the Isolated Midgut of Hyalophora Cecropia

1971 ◽  
Vol 54 (1) ◽  
pp. 269-274
Author(s):  
W. R. HARVEY ◽  
K. ZERAHN
Keyword(s):  
Active Transport ◽  
Sodium Transport ◽  
Transport Mechanism ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Large Current ◽  
Sodium Flux ◽  
Hyalophora Cecropia ◽  
Sodium Solution

1. Sodium and lithium are actively transported by the isolated midgut of Hyalophora cecropia. 2. The short-circuit current in 32 mM sodium solution is about half of that in 32 mM potassium solution. 3. The sodium flux measured with 22Na from blood-side to lumen accounts for all of the short-circuit current and is 19 times the flux from lumen to blood-side. 4. In a solution containing 16 mM potassium and 16 mM sodium there is no transport of sodium, although a large current remains. 5. The sodium transport mechanism is not sensitive to ouabain.

scholarly journals IONIC TRANSFER ACROSS THE ISOLATED FROG LARGE INTESTINE

1959 ◽  
Vol 42 (3) ◽  
pp. 461-473 ◽  
Author(s):  
I. L. Cooperstein ◽  
C. Adrian M. Hogben
Keyword(s):  
Active Transport ◽  
Large Intestine ◽  
Short Circuit ◽  
Flux Ratio ◽  
Short Circuit Current ◽  
Considerable Proportion ◽  
Ionic Transfer ◽  
Serosal Surface ◽  
Net Flux ◽  
Unidirectional Fluxes

The unidirectional fluxes of sodium, chloride, and of the bicarbonate and CO2 pair were determined across the isolated large intestine of the bullfrog, Rana catesbiana. The isolated large intestine of the frog is characterized by a mean transmembrane potential of 45 mv., serosal surface positive with respect to mucosal. The unidirectional sodium flux from mucosal to serosal surface was found to be equal to the short-circuit current, thus the net flux was less than the simultaneous short-circuit current. This discrepancy between active sodium transport and short-circuit current can be attributed to the active transport of cation in the same direction as sodium and/or the active transport of anion in the opposite direction. The unidirectional fluxes of chloride and the bicarbonate and CO2 pair revealed no evidence for active transport of either anion. A quantitative study of chloride fluxes at 45 mv. revealed a flux ratio of 1.8 which is considerably less than a ratio of 6 expected for free passive diffusion. It was concluded that a considerable proportion of the isotopic transfer of chloride could be attributed to "exchange diffusion." Study of the electrical properties of the isolated frog colon reveals that it can be treated as a simple D. C. resistance over the range of -20 to +95 mv.

Ion transport in isolated cornea of the rabbit

1965 ◽  
Vol 209 (6) ◽  
pp. 1311-1316 ◽  
Author(s):  
K. Green
Keyword(s):  
Ion Transport ◽  
Active Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Ringer Solution ◽  
Initial Value ◽  
Rabbit Cornea ◽  
Flux Measurements ◽  
Net Flux ◽  
Normal Ringer

When the isolated rabbit cornea is bathed with well-stirred normal Ringer solution, only a low potential difference (PD) exists across the tissue; the initial value of 2 mv rises to 6 mv (endothelium positive) 1 hr after excision from the animal. In sodium-free Ringer solution the PD becomes negative before becoming negligible, while in chloride-free Ringer the PD rises to triple the value in normal Ringer. Flux measurements of sodium 22 show that there is an initial inequality between the net flux and the measured short-circuit current (SCC), the values of which become equal 1 hr after removal of the cornea from the animal Flux measurements of chloride 36 during this 1st hr indicate an active transport of chloride inward across the cornea, but after 1 hr the fluxes are equal in each direction. The differences of the net currents generated by the sodium and chloride transports equal the measured SCC, and the two transports have been shown to be able to exist independently.

Active transport of magnesium across the isolated midgut of Hyalophora cecropia

1975 ◽  
Vol 63 (2) ◽  
pp. 313-320
Author(s):  
J. L. Wood ◽  
A. M. Jungreis ◽  
W. R. Harvey
Keyword(s):  
Steady State ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Potassium Transport ◽  
Magnesium Concentration ◽  
Magnesium Transport ◽  
Wet Weight ◽  
Net Flux ◽  
Burk Plot

1. The 28Mg-measured net flux of magnesium from lumen-side to haemolymph-side of the isolated and short-circuited midgut was 1.97 +/− 0.28 mu-equiv cm(−2) /(−1) in 8 mM-Mg2+. 2. The magnesium-influx shows a delay before the tracer steady-state is attained, indicating the existence of a magnesium-transport pool equivalent to 6.7 mu-equiv/g wet weight of midgut tissue. 3. Magnesium depresses the short-circuit current produced the midgut but not the potassium transport, the depression being equal to the rate of magnesium transport. 4. Magnesium transport yields a linear Lineweaver-Burk plot with an apparent Km of 34 mM-Mg2+ and an apparent Vmax of 14.9 mu-equiv cm(−1) /(−1). 5. Magnesium is actively transported across the midgut and contributes to the regulation of the haemolymph magnesium concentration in vivo.

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.

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.

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