scholarly journals Intracellular Electrical Potentials in Frog Skin

1965 ◽  
Vol 48 (4) ◽  
pp. 543-557 ◽  
Author(s):  
Marcelino Cereijido ◽  
Peter F. Curran
Keyword(s):  
Frog Skin ◽  
Marked Decrease ◽  
Ionic Composition ◽  
Acta Physiol ◽  
Intracellular Potential ◽  
Ringer’S Solution ◽  
Electrical Potentials ◽  
K Concentration

The influence of changes in ionic composition of the bathing solutions on intracellular electrical potentials in frog skin has been examined. When the skin bathed in SO4 Ringer's solution is penetrated with a microelectrode two approximately equal potential jumps were frequently observed and most experiments were carried out with the electrode located between these steps. Substitution of Cl for SO4 in the bathing solutions caused a decrease in PD across both the "outer" and "inner" barriers. When the skin was short-circuited an average intracellular potential of -18 mv was found with both Cl and SO4 Ringer's. With the skin in SO4 Ringer's, decrease in Na concentration of the outside solution caused a decrease in PD between the microelectrode and the outside solution which was approximately the same as the decrease in total skin PD. With SO4 Ringer's, an increase in K concentration in the inside solution caused a marked decrease in total skin PD. However, only 50 per cent of this change occurred at the inner barrier, between the microelectrode and the inside solution. The remainder of the change occurred at the outer barrier. This observation does not appear to be consistent with the model of the skin proposed by Koefoed-Johnson and Ussing (Acta Physiol. Scand., 1958, 42, 298).

scholarly journals Na Transport across Frog Skin at Low External Na Concentrations

1966 ◽  
Vol 49 (6) ◽  
pp. 1161-1176 ◽  
Author(s):  
THOMAS U. L. BIBER ◽  
RONALD A. CHEZ ◽  
PETER F. CURRAN
Keyword(s):  
Frog Skin ◽  
Short Circuit ◽  
Electrical Potential ◽  
Short Circuit Current ◽  
Open Circuit ◽  
Potential Profile ◽  
Na Transport ◽  
Ringer’S Solution ◽  
Electrical Potentials ◽  
Single Compartment

Isolated frog skin was bathed with a dilute solution containing 1 mm NaCl on the outside and with normal Ringer’s solution on the inner surface. Net Na flux was determined by simultaneous measurement of unidirectional fluxes with Na22 and Na24 and intracellular electrical potentials were examined with microelectrodes. There was a net inward transport of Na under both open-circuit and short-circuit conditions. The short-circuit current was approximately 15% greater than the net Na flux; the discrepancy could be accounted for by a small outward flux of Cl. The electrical potential profile did not differ greatly from that observed in skins bathed on the outside with normal Ringer’s solution. Under open-circuit conditions, there were usually several potential steps and under short-circuit conditions the cells were negative relative to the bathing solutions. Estimates of epithelial Na concentrations utilizing radioactive Na suggested that if all epithelial Na were in a single compartment, an active entry step would be necessary to allow a net inward Na transport. The results could also be explained by a series arrangement of Na compartments without necessarily postulating an active Na entry. The behavior of the potential profile suggested that this latter alternative was more likely.

scholarly journals The Effects of Alkali Metal Cations and Common Anions on the Frog Skin Potential

1964 ◽  
Vol 47 (4) ◽  
pp. 749-771 ◽  
Author(s):  
Barry D. Lindley ◽  
T. Hoshiko
Keyword(s):  
Alkali Metal ◽  
Frog Skin ◽  
Ionic Composition ◽  
Metal Cations ◽  
Leopard Frog ◽  
Constant Field ◽  
Alkali Metal Cations ◽  
Ionic Selectivity ◽  
Skin Potential ◽  
Mean Values

The effects on the potential difference across isolated frog skin (R. catesbeiana, R. pipiens) of changing the ionic composition of the bathing solutions have been examined. Estimates of mean values and precision are presented for the potential changes produced by substituting other alkali metal cations for Na at the outside border and for K at the inside border. In terms of ability to mimic Na at the outside border of bullfrog skin, the selectivity order is Li > Rb, K, Cs; at the outside border of leopard frog skin, Li > Cs, K, Rb. In terms of ability to mimic K at the inside border of bullfrog and leopard frog skin: Rb > Cs > Li > Na. Orders of anion selectivity in terms of sensitivity of the potential for the outside border of bullfrog skin are Br > Cl > NO3 > I > SO4, isethionate and of leopard frog skin are Br, Cl > I, NO3, SO4. An effect of the solution composition (ionic strength?) on the apparent Na-K selectivity of the outside border is described. The results of the investigation have been interpreted and discussed in terms of the application of the constant field equation to the Koefoed-Johnsen-Ussing frog skin model. These observations may be useful in constructing and testing models of biological ionic selectivity.

scholarly journals Permafrost coverage, watershed area and season control of dissolved carbon and major elements in western Siberian rivers

2015 ◽  
Vol 12 (21) ◽  
pp. 6301-6320 ◽  
Author(s):  
O. S. Pokrovsky ◽  
R. M. Manasypov ◽  
S. Loiko ◽  
L. S. Shirokova ◽  
I. A. Krickov ◽  
...  
Keyword(s):  
Environmental Factors ◽  
Western Siberia ◽  
Ionic Composition ◽  
Major Elements ◽  
Plant Litter ◽  
Permafrost Zone ◽  
Small Rivers ◽  
Watershed Area ◽  
Dissolved Carbon ◽  
K Concentration

Abstract. Analysis of organic and inorganic carbon (DOC and DIC, respectively), pH, Na, K, Ca, Mg, Cl, SO4 and Si in ~ 100 large and small rivers (< 10 to ≤ 150 000 km2) of western Siberia sampled in winter, spring, and summer over a more than 1500 km latitudinal gradient allowed establishing main environmental factors controlling the transport of river dissolved components in this environmentally important region, comprising continuous, discontinuous, sporadic and permafrost-free zones. There was a significant latitudinal trend consisting in a general decrease in DOC, DIC, SO4, and major cation (Ca, Mg, Na, K) concentration northward, reflecting the interplay between groundwater feeding (detectable mostly in the permafrost-free zone, south of 60° N) and surface flux (in the permafrost-bearing zone). The northward decrease in concentration of inorganic components was strongly pronounced both in winter and spring, whereas for DOC, the trend of concentration decrease with latitude was absent in winter, and less pronounced in spring flood than in summer baseflow. The most significant decrease in K concentration from the southern (< 59° N) to the northern (61–67° N) watersheds occurs in spring, during intense plant litter leaching. The latitudinal trends persisted for all river watershed size, from < 100 to > 10 000 km2. Environmental factors are ranked by their increasing effect on DOC, DIC, δ13CDIC, and major elements in western Siberian rivers as follows: watershed area < season < latitude. Because the degree of the groundwater feeding is different between large and small rivers, we hypothesize that, in addition to groundwater feeding of the river, there was a significant role of surface and shallow subsurface flow linked to plant litter degradation and peat leaching. We suggest that plant-litter- and topsoil-derived DOC adsorbs on clay mineral horizons in the southern, permafrost-free and discontinuous/sporadic permafrost zone but lacks the interaction with minerals in the continuous permafrost zone. It can be anticipated that, under climate warming in western Siberia, the maximal change will occur in small (< 1000 km2 watershed) rivers DOC, DIC and ionic composition and this change will be mostly pronounced in summer.

scholarly journals EFFECTS OF METABOLIC INHIBITORS AND DRUGS ON ION TRANSPORT AND OXYGEN CONSUMPTION IN ISOLATED FROG SKIN

1957 ◽  
Vol 41 (2) ◽  
pp. 397-417 ◽  
Author(s):  
Ernst G. Huf ◽  
Norma S. Doss ◽  
Joyce P. Wills
Keyword(s):  
Ion Transport ◽  
Frog Skin ◽  
Ionic Composition ◽  
Diethyl Malonate ◽  
Metabolic Inhibitors ◽  
Chemical Agent ◽  
O2 Consumption ◽  
Nacl Transport ◽  
Exchange Adsorption ◽  
Active Ion Transport

Active ion (NaCl) transport across isolated frog skin is discussed in relation to sodium and potassium composition and to O2 consumption of skin. A distinction is made between processes in skin related to "unidirectional active ion transport" and processes related to "maintenance electrolyte equilibrium;" i.e., ionic composition of skin. Several metabolic inhibitors were found that could be used in separating maintenance electrolyte equilibrium from unidirectional active ion transport. Fluoroacetate (up to 1 x 10–2M/liter) did not affect maintenance electrolyte equilibrium, but severely diminished the rate of active ion transport. This could also be accomplished with azide and diethyl malonate when 1 x 10–3 molar concentrations were used. When applied in higher concentrations, these two inhibitors, and several others, diminished active ion transport, but this was associated with changes in maintenance electrolyte equilibrium (gain of Na+ by and loss of K+ from skin). Similar observations were made when skins were subjected to K+-deficient media. Mersalyl and theophylline, in low concentrations, stimulated active ion transport without leading to changes in maintenance electrolyte equilibrium. Inhibition of active ion transport was found accompanied by decrease, increase, and unaltered over-all O2 consumption, depending on the kind of chemical agent used. A provisional scheme of the mechanism of unidirectional active ion transport is proposed. It is conceived as a process of metabolically supported ion exchange adsorption, involving a carrier, forming complexes with K+ and Na+, a trigger, K+ ions, and two spatially separated metabolic pathways.

Potassium transport in the freshwater bivalve Dreissena polymorpha

1995 ◽  
Vol 198 (4) ◽  
pp. 861-868 ◽  
Author(s):  
S Wilcox ◽  
T Dietz
Keyword(s):  
Dreissena Polymorpha ◽  
Ionic Composition ◽  
Potassium Transport ◽  
Freshwater Bivalve ◽  
Bathing Medium ◽  
Potassium Influx ◽  
K Concentration ◽  
Solute Composition ◽  
Total Tissue ◽  
K Depletion

Potassium transport and blood ion composition were examined in the freshwater bivalve Dreissena polymorpha. Animals acclimated to artificial pondwater (APW, [K+]=0.05 mmol l-1) for 4 weeks gradually lost Na+ and Cl-, but the blood K+ concentration remained constant near 0.5 mmol l-1. Blood [K+] in D. polymorpha declined by 41 % after 1 week of exposure to K+-free APW. Conversely, blood [K+] rose to 1.52&plusmn;0.05 mmol l-1 (mean &plusmn; s.e.m.) 24 h after exposure to 0.5 mmol l-1 K+ APW. Total tissue K+ content remained stable in animals maintained in APW, but fell significantly in animals exposed to K+-free APW for 2 weeks. The net K+ flux (Jnet) for animals incubated in APW, with an average K+ concentration of 0.07 mmol l-1, was -0.27&plusmn;0.06 &micro;equiv g-1 dry tissue h-1, significantly different from the value of 0.50&plusmn;0.08 &micro;equiv g-1 dry tissue h-1 for animals transferred to 0.30 mmol l-1 K+ APW. A transepithelial membrane potential of -3.6&plusmn;0.7 mV (blood negative compared with the bathing medium) was measured in APW-acclimated mussels. Potassium influx was measured with 42K and displayed Michaelis&shy;Menten saturation kinetics at dilute K+ concentrations. The Km was 0.084&plusmn;0.054 mmol l-1 and the Jmax was 1.74&plusmn;0.39 &micro;equiv g-1 dry tissue h-1. Both the Km and Jmax for animals exposed to K+-free APW for 7 days were unchanged. Using 86Rb, qualitatively similar transport characteristics were observed for animals incubated in K+-free, Rb+ APW, but the 22 day K+ depletion time significantly increased Jmax. D. polymorpha compensated for changes in the ionic composition of the acclimation medium by tolerating alterations in blood solute composition and adjusting ion transport rates.

scholarly journals On the distribution of Na+ pump sites in the frog skin

1977 ◽  
Vol 75 (3) ◽  
pp. 968-973 ◽  
Author(s):  
JW Mills ◽  
DR DiBona
Keyword(s):  
Binding Sites ◽  
Living Cell ◽  
Frog Skin ◽  
Cell Layer ◽  
Ouabain Binding ◽  
Ringer’S Solution ◽  
Na Pump ◽  
Stratum Spinosum ◽  
Sufficient Concentration ◽  
Sustained Increase

Exposure of the outside of the isolated frog skin to a Ringer's solution, made hypertonic by the addition of mannitol, causes a rapid and sustained increase in transepithelial permeability through a structural distortion-a focal blistering-of the "tight" junctions of the outermost living cell layer. [(3)H]ouabain, used as an autoradiographic marker for the Na+-pump (Na+-K+-adenosine triphosphatase), is usually unable to penetrate the frog skin from the outside solution, but when added to a hypertonic mannitol- Ringer's solution in the outside bath it readily penetrates the epithelium, presumably through the opened shunt pathway. Radioautographic analysis of [(3)H]ouabain binding sites revealed that most of ouabain enters from the outside solution binds to the sites on the cell membranes of the stratum spinosum, as was the case when it was applied from the inside bath in an earlier study. The outer living cell layer, the first to be exposed to ouabain, does not appear to be the major site for the Na+-pump, and therefore, is not likely to be responsible for most of the active pumping of Na+. This result demonstrates that previous failure to show a high density of Na+-pump sites on the cells of the outermost layer, when [(3)H]ouabain was applied from the inside solution, was not due to the inability of the marker to reach these cells at a sufficient concentration to reveal all pump sites. These results provide further support for a model of Na+-transport across the frog skin which distributes the active pump step on the inward facing membranes of all living cells.

scholarly journals Electrical Excitability of Isolated Frog Skin and Toad Bladder

1964 ◽  
Vol 47 (3) ◽  
pp. 545-565 ◽  
Author(s):  
Alan Finkelstein
Keyword(s):  
Plasma Membrane ◽  
Action Potential ◽  
Frog Skin ◽  
Ionic Composition ◽  
Toad Bladder ◽  
Metabolic Inhibitors ◽  
Electrical Excitability ◽  
Msec Duration ◽  
Sufficient Intensity ◽  
Solution Bathing

When current of proper polarity and sufficient intensity is passed across isolated frog skin or toad bladder, an action potential of about 200 mv and 10 msec. duration with a sharp threshold and refractory period of several seconds' duration is elicited. Interruption of current during the action potential abolishes the response, and, as shown by appropriate bridge measurements, this occurs because the action potential results from resistance variations during the current flow. The ionic composition of the medium bathing the frog skin was varied, and it was found that the response is relatively insensitive to changes in the solution bathing the inner surface, but rapidly and reversibly affected by changes in the outer solution, particularly by replacement of sodium with potassium and by variations of calcium concentration. It was also observed that the resistance of the skin and action potential across it are reversibly altered by metabolic inhibitors and that these alterations occur independently of any changes in the intrinsic EMF of the system. From the finding that the action potential across frog skin and toad bladder results from a time-variant resistance, it is argued that this same phenomenon can be the basis of electrical excitability in general. This would attribute physical significance to the equivalent circuit commonly employed to represent the plasma membrane; i.e., the plasma membrane would be a mosaic structure of spatially separate permselective regions.

Ionic composition of red cells in fetal, newborn, and adult sheep

1961 ◽  
Vol 201 (1) ◽  
pp. 85-88 ◽  
Author(s):  
Jack N. Blechner
Keyword(s):  
Post Partum ◽  
Ionic Composition ◽  
Red Cells ◽  
The Other ◽  
Flame Photometry ◽  
Adult Sheep ◽  
K Concentration ◽  
Dissociation Curves ◽  
The Relationship

The concentrations of Na and K in the erythrocytes of the blood of adult, purebred Dorset ewes and their fetuses were determined by flame photometry. With respect to these cations, adult ewes can be divided into two groups; in one, Na is in higher concentration and, in the other, K concentration is higher. In every fetus studied, however, the K concentration exceeded the Na, and there was a higher K and a lower Na concentration than in the maternal erythrocytes. In lambs of mothers with a high Na concentration in their erythrocytes, the transition from the fetal to the adult electrolyte pattern was completed 7 or 8 weeks post partum. The relationship between the ionic composition of the red cells and the O2 dissociation curves in mothers and their fetuses, and in both groups of adult sheep, is discussed. Differences in the concentrations of Na and K in the erythrocytes do not appear to explain the differences in O2 dissociation curves observed among adult sheep.

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