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.

Osmotic Regulation in the Green Toad (Bufo Viridis)

1962 ◽  
Vol 39 (2) ◽  
pp. 261-270 ◽  
Author(s):  
MALCOLM S. GORDON
Keyword(s):  
Body Weight ◽  
Body Fluid ◽  
Short Circuit ◽  
Electrical Potential ◽  
Inorganic Ions ◽  
Short Circuit Current ◽  
Urine Concentration ◽  
Bufo Viridis ◽  
Green Toad ◽  
Toad Bufo

1. The osmotic and ionic regulatory abilities of adults of a freshwater population of the green toad (Bufo viridis) have been studied. These toads tolerated environmental salinities as high as 19% at temperatures near 25° C. Two individuals of another population of this species tolerated salinities as high as 23% 2. Changes in body weight of toads transferred to different environmental salinities indicate that the skin of this form is permeable to water. Rapid return to control levels of body weight indicate that drinking of external medium may be an important part of the initial adjustment to high salinities. 3. Above salinities of about 8% plasma Δ rises with increasing environmental Δ. Marked hypertonicity of the plasma is maintained in low salinities, but isotonicity with the medium is approached in higher salinities. Increases in plasma concentration above freshwater levels are due primarily to increased NaCl concentration (about 84%), partly to increased concentrations of urea (5-10%) and other osmotically active substances. 4. Urinary Δ is much lower than plasma Δ in dilute media, but becomes identical with plasma Δ above salinities of about 15%. Increases in urine concentration above freshwater levels are also due primarily to NaCl increase (74%). Considerable quantities of salt are lost via the urine. The kidneys seem to lose much of their ability to regulate urinary salt concentrations in high-salinity media. 5. Measurements of electrical potential and short-circuit current indicate that active uptake of inorganic ions by the skin continues in concentrated media, but at reduced rates. 6. Changes in muscle water, Na and K contents indicate the occurrence of some redistribution of water and salts between various body-fluid compartments as part of the salinity adaptation process. 7. In preference experiments, B. viridis chooses the land over any aquatic environment. Among aquatic environments it prefers those with salinities below 8%. 8. When combined with some earlier data by other workers who studied other populations of B. viridis, the present data indicate great uniformity of ionic and osmotic regulatory abilities among populations of this species. The marked differences between salinity tolerances of different populations are indicated to be due to differences in tissue tolerance of high body-fluid salinities.

Effect of furosemide on the electrical parameters of frog skin

1982 ◽  
Vol 243 (6) ◽  
pp. F581-F587 ◽  
Author(s):  
A. Corcia ◽  
S. R. Caplan
Keyword(s):  
Active Transport ◽  
Frog Skin ◽  
Short Circuit ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Relative Increase ◽  
Electrical Potential Difference ◽  
Electrical Parameters ◽  
Active Conductance ◽  
Solution Bathing

When added to the mucosal solution bathing isolated frog skin at concentrations ranging from 5 X 10(-4) to 3 X 10(-3) M, the diuretic furosemide increased both the active transport of sodium and the electrical potential difference across the tissue in a dose-dependent way. The same effect was observed in chloride-free solutions. Mucosal furosemide also decreased the passive unidirectional fluxes of chloride. We believe that as far as electrical parameters are concerned mucosal furosemide has a double effect in frog skin: it increases the active conductance to sodium across the mucosal membrane, thus increasing active transport, and decreases the passive permeability to chloride, thus altering the passive conductance of the skin. The relative increase in short-circuit current was, however, invariably greater than the increase of the active conductance, suggesting the influence of yet a third effect. The effect of mucosal furosemide on active sodium transport was blocked by amiloride (5 X 1-(-5) M) and was independent of vasopressin. Qualitatively the effect was similar to the effect produced by triphenylmethylphosphonium ion.

Electrical and transport characteristics of skin of larval Rana catesbeiana

1979 ◽  
Vol 237 (1) ◽  
pp. R74-R79 ◽  
Author(s):  
T. C. Cox ◽  
R. H. Alvarado
Keyword(s):  
Rana Catesbeiana ◽  
Short Circuit ◽  
Electrical Potential ◽  
Flux Ratio ◽  
Short Circuit Current ◽  
Ringer Solution ◽  
Open Circuit ◽  
Shunt Resistance ◽  
Ion Substitution ◽  
Adult Skin

Carefully dissected, mounted, and bathed with Ringer solution, the larval bullfrog skin has a resistance of about 9,000 omega.cm2 and a stable transepithelial electrical potential of about 20 mV (inside +). A short-circuit current of about 2 microA.cm-2 is generated that is comparable in magnitude to the net inward flux of Na+. At open circuit the flux ratio equation for Na+ is not satisfied. Larval skin is less sensitive to ouabain, amiloride, and ADH than adult skin. The current-voltage (C-V) relationship across the preparation is not linear; there are distinct breaks in both the hyperpolarizing and hypopolarizing regions. The former break, at about +130 mV, corresponds with a break observed in adult skin that corresponds with ENa. The shunt resistance (RS) and active pathway resistance (RA) were estimated by C-V curve analysis and by ion substitution. The two methods yielded comparable values with RS about 11 k omega.cm2 and RA about 62 k omega.cm2. It is suggested that transport is limited by the number of entry sites for sodium at the apical border of transport cells.

Nystatin studies of the skin of larval Rana catesbeiana

1983 ◽  
Vol 244 (1) ◽  
pp. R58-R65
Author(s):  
T. C. Cox ◽  
R. H. Alvarado
Keyword(s):  
Rana Catesbeiana ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Ringer Solution ◽  
Electrical Characteristics ◽  
Shunt Resistance ◽  
Selective Permeability ◽  
Ion Substitution

Transport and electrical characteristics of the isolated skin of larval Rana catesbeiana were analyzed using ion substitution and nystatin. When the inner (IBS) and outer (OBS) bathing solutions contained Na Ringer solution the electrical potential (TEP), short-circuit current (SCC), and resistance (R2) were 23.5 +/- 7.0 mV, 2.8 +/- 0.7 microA . cm-2, and 8.00 +/- 0.74 k omega. cm2, respectively (n = 4). When K was substituted for Na in the OBS these values were not changed significantly. When nystatin (120 U.cm-3), a drug that increases the permeability of membranes to small cations, was added to the OBS (Na Ringer) there was a striking increase in the TEP to 52.8 +/- 3.1 mV, SCC to 14.8 +/- 2.0 microA . cm-2, and drop in R2 to 3.75 +/- 0.52 k omega . cm2. The response to nystatin was similar with Na or K Ringer solution in the OBS (Na Ringer in the IBS). With Na Ringer in the OBS and IBS, the increase in SCC induced by low doses of nystatin equaled net Na flux measured isotopically. Plots of transepithelial conductance against SCC after nystatin were linear and provided estimates of shunt resistance (R*sh = 14.6 +/- 1.3 k omega . cm2) and electromotive driving force for ions (E*A = 76 +/- 3 mV). Similar curves were obtained with K Ringer in the OBS. In the presence of nystatin, characteristics of the basolateral membrane were evaluated. It displayed selective permeability to K relative to Na or Tris.

Potassium secretion by nonsensory region of gerbil utricle in vitro

1987 ◽  
Vol 253 (4) ◽  
pp. F613-F621 ◽  
Author(s):  
N. Y. Marcus ◽  
D. C. Marcus
Keyword(s):  
Short Circuit ◽  
Control Level ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Ringer Solution ◽  
Electrical Potential Difference ◽  
Free Solution ◽  
K Secretion

The isolated nonsensory region of the gerbil utricle in vitro produced a lumen-positive transepithelial electrical potential difference (VT) of +5.7 mV and a luminal fluid containing 106 mM K when bathed in mammalian Ringer solution (5 mM K and 150 mM Na). The lumen of this region was perfused in vitro with K-free solution and the luminal [K], VT, and transepithelial resistance (RT) were measured before and following perfusion under control conditions and after addition of bumetanide (0.1 mM) or ouabain (1 mM) to the bath. The perfusate contained a reduced [Ca], since the average value of utricular endolymph in vivo (0.28 +/- 0.03 mM) measured with Ca-selective microelectrodes was 38% of that in perilymph. Under control conditions, the luminal [K] initially increased at a rate of 2.13 mumol X cm-2 X h-1 after perfusion; net secretion continued until the luminal [K] returned to its preperfusion level. This flux rate corresponds to 57 microA/cm2. The “equivalent short-circuit current” (Equiv. Isc; VT/RT) was found to average 61 microA/cm2. Both K secretion and VT were fully inhibited by bumetanide and by ouabain. Luminal application of Ba (5 mM) in K-free solution had no effect on the initial rate of K secretion, but did prevent full recovery of luminal [K] to the control level. These results are the first estimates of K secretion by the nonsensory cells of the utricle and are the first to directly demonstrate inhibition of K secretion in the inner ear by bumetanide and in the nonsensory tissue of the utricle by ouabain.

Effects of amphotericin B on ionic transport and sodium permeability of the toad lens

1975 ◽  
Vol 229 (6) ◽  
pp. 1520-1525 ◽  
Author(s):  
PJ Bentley ◽  
OA Candia
Keyword(s):  
Amphotericin B ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Ringer Solution ◽  
Anterior Surface ◽  
Sodium Permeability ◽  
Solution Bathing ◽  
Net Flux ◽  
Large Decline

The polyene antibiotic amphotericin B decreases the PD and short-circuit current (SCC) across the amphibian lens in vitro. It was only effective when placed in the solution at the anterior side and its effect was reversible. Amphotericin B caused a large decline in the PD across the anterior surface of the lens and a smaller reduction in the PD across the posterior side. This seems to be due to a direct decrease of the electrical resistance of the anterior face. The effects required the presence of sodium in the Ringer solution bathing the anterior surface. The translenticular Na fluxes were increased in both directions so that the net flux changed little. Amphotericin B produced a considerable increase in the rate of accumulation of sodium and loss of potassium by the lens. The oxygen consumption of the lens was unchanged by amphotericin B. Amphotericin B appears to act on the lens epithelium by selectively increasing its passive sodium permeability.

OSMOTIC INHIBITION OF THE NATRIFERIC RESPONSE OF THE TOAD URINARY BLADDER TO VASOPRESSIN

1975 ◽  
Vol 67 (1) ◽  
pp. 119-125
Author(s):  
P. J. BENTLEY
Keyword(s):  
Urinary Bladder ◽  
Water Movement ◽  
Short Circuit ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Toad Bladder ◽  
Toad Urinary Bladder ◽  
Electrical Potential Difference ◽  
Osmotic Gradient

SUMMARY The electrical potential difference and short-circuit current (scc, reflecting active transmural sodium transport) across the toad urinary bladder in vitro was unaffected by the presence of hypo-osmotic solutions bathing the mucosal (urinary) surface, providing that the transmural flow of water was small. Vasopressin increased the scc across the toad bladder (the natriferic response), but this stimulation was considerably reduced in the presence of a hypo-osmotic solution on the mucosal side, conditions under which water transfer across the membrane was also increased. This inhibition of the natriferic response did not depend on the direction of the water movement, for if the osmotic gradient was the opposite way to that which normally occurs, the response to vasopressin was still reduced. The natriferic response to cyclic AMP was also inhibited in the presence of an osmotic gradient. Aldosterone increased the scc and Na+ transport across the toad bladder but this response was not changed when an osmotic gradient was present. The physiological implications of these observations and the possible mechanisms involved are discussed.

Active electrolyte transport in mammalian buccal mucosa

1988 ◽  
Vol 255 (3) ◽  
pp. G286-G291 ◽  
Author(s):  
R. C. Orlando ◽  
N. A. Tobey ◽  
V. J. Schreiner ◽  
R. D. Readling
Keyword(s):  
Buccal Mucosa ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Electrolyte Transport ◽  
Electrical Potential Difference ◽  
Ussing Chambers ◽  
Net Fluxes

The transmural electrical potential difference (PD) was measured in vivo across the buccal mucosa of humans and experimental animals. Mean PD was -31 +/- 2 mV in humans, -34 +/- 2 mV in dogs, -39 +/- 2 mV in rabbits, and -18 +/- 1 mV in hamsters. The mechanisms responsible for this PD were explored in Ussing chambers using dog buccal mucosa. After equilibration, mean PD was -16 +/- 2 mV, short-circuit current (Isc) was 15 +/- 1 microA/cm2, and resistance was 1,090 +/- 100 omega.cm2, the latter indicating an electrically "tight" tissue. Fluxes of [14C]mannitol, a marker of paracellular permeability, varied directly with tissue conductance. The net fluxes of 22Na and 36Cl were +0.21 +/- 0.05 and -0.04 +/- 0.02 mueq/h.cm2, respectively, but only the Na+ flux differed significantly from zero. Isc was reduced by luminal amiloride, serosal ouabain, or by reducing luminal Na+ below 20 mM. This indicated that the Isc was determined primarily by active Na+ absorption and that Na+ traverses the apical membrane at least partly through amiloride-sensitive channels and exits across the basolateral membrane through Na+-K+-ATPase activity. We conclude that buccal mucosa is capable of active electrolyte transport and that this capacity contributes to generation of the buccal PD in vivo.

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.

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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