Influence of vasopressin and amiloride on shunt pathways of frog skin

O'Neil, R. G.; Helman, S. I.

doi:10.1152/ajplegacy.1976.231.1.164

Cited by 23 publications

(15 citation statements)

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“…In accordance with results ofO'Neill & Helman (1976), essentially no changes of E1 from the value of 120mV in the control period were observed under the influence of ADH or Amiloride in addition to ADH. In contrast, E[ decreased from the control value of 99 mV until Summary of the effect of ADH upon the resistance of the transcellular pathway, RN~, and the resistance of the outer and inner border, R o and R~…”

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confidence: 90%

Effects of antidiuretic hormone upon electrical potential and resistance of apical and basolateral membranes of frog skin

Nagel

1978

J. Membrain Biol.

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The effect of ADH upon the intracellular potential and the resistance of inner and outer borders of the transport pathway was investigated on isolated skins of Rana temporaria. Within 40 min after ADH (100--300 mU/ml), the intracellular potential under short-circuit conditions decreased to about 40% of the control value (--79 +/- 4 mV), concomitant with an increase in the short-circuit current to about 160% of the control value. Amiloride, applied when steady values under ADH had been reached, caused an immediate rise of the intracellular potential to values typical for control conditions. This confirms (i) the intracellular location of the microelectrode and the absence of impalement artifacts, and (ii) the ineffectiveness of ADH upon the electromotive forces of the inner border. ADH had no effect upon the intracellular potential after blockage of the Na entry by Amiloride. The equilibrium potential of the outer border was estimated to be about +20mV under the influence of ADH. As this value is considerably less positive than might be expected for the chemical potential of Na, a significant contribution of ions other than Na to the outer border conductance and equilibrium potential is implicated. The resistance of the outer border was more significantly decreased than that of the active transcellular pathway after ADH due to an increase in the inner border resistance, which exceeded that of the outer border after ADH. The effect of ADH upon the outer membrane characteristics would be underestimated by a factor of two, if the alterations of the electrical potential difference were not taken into consideration.

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confidence: 90%

Effects of antidiuretic hormone upon electrical potential and resistance of apical and basolateral membranes of frog skin

Nagel

1978

J. Membrain Biol.

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“…(1). Similar conclusions have been drawn for frog skin (O'Neil & Helman, 1976). 7 is based on a number of assumptions (Appendix).…”

Section: The I-v Relation Of the Sodium Entry Stepsupporting

confidence: 71%

The electrophysiology of rabbit descending colon

Thompson¹,

Suzuki²,

Schultz³

1982

J. Membrain Biol.

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A method is described for determining the "'instantaneous" transepithelial current-voltage (I-V) relations across rabbit descending colon and deriving the f-V relatior~s of the amiloride-sensitive Na-entry step across the apical membrane. The latter conforms closely to the predictions of the Goldman-Hodgkin-Katz "constant-field" flux equation over a wide range of values of the transapical electrical potential difference (-120 to +50 mV), suggesting that Na entry is the result of simple electrodiffusion through homogeneous pores or channels. The permeability of the apical membrane to Na averaged 0.012cm/hr, and the intracellular Na activity averaged 10mM. In these studies, the rate of Na entry across the apical membrane varied, spontaneously, over a fourfold range; this variation is entirely attributable to parallel variations in the partial conductance of the apical membrane to Na with no change in the driving force for this movement.Bathing the serosal surface of the tissue with a high-K solution abolishes the electrical potential difference across the basolateral membrane and markedly reduces the resistance of that barrier. Under these conditions, the I-V relations of the amiloridesensitive Na-entry step across the apical membrane also conform closely to the predictions of the "constant-field" flux equation.Finally, the significance of the point at which the transepitheliai I-V relations in the absence and presence of arniloride intersect ("EN,") and the origin of the "bends" in these I-V relations at or around this point are discussed. We demonstrate that the point of intersection is simply that value of the transepithdial electrical potential difference at which Na entry is abolished and has no direct bearing on the energetics of the basolateral pump. The "bend" in the I-V relations appears to be due to an increase in the conductance of a pathway in the apical membrane that parallels the Na-entry pathway as well as an increase in the conductance of the paracellular pathway; thus, this "bend" does not appear to be directly related to changes in the "active Na transport pathway". Key words colon 9 Na entry , electrophysiology 9 currentvoltage relations 9 apical membrane -amiloride

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“…Having found Rs, the transcellular resistance to sodium current (RNa) was calculated as described previously (O'Neil & Helman, 1976) as follows: RNa = (Rt Rs)/(Rs-R ).…”

Section: Methodsmentioning

confidence: 99%

“…(3) and the further equation using amiloride to change only the value of Ra: s =R(a'R+ 1 R-R'(c + 1)' where the prefix 'denotes measurement in presence of amiloride. Having found Rs, the transcellular resistance to sodium current (RNa) was calculated as described previously (O'Neil & Helman, 1976) as follows: RNa = (Rt Rs)/(Rs-R ).…”

Section: Introductionmentioning

confidence: 99%

Sodium‐selective micro‐electrode study of apical permeability in frog skin: effects of sodium, amiloride and ouabain.

Harvey¹,

Kernan²

1984

The Journal of Physiology

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SUMMARY1. The intracellular sodium ion activity (aia), apical membrane potential ('ac) and apical sodium electrochemical driving force (ARilN) in Rana temporaria skin were measured using double-barrelled sodium-sensitive micro-electrodes, in the presence of various apical sodium activities (aNa), amiloride, ouabain, and during voltage clamp of 0ac.2. The permeability and specific conductance of the apical cell membrane to sodium entry (pa and GNa respectively) were calculated from the GoldmanHodgkin-Katz equation and the Nernst-Planck (electrodiffusion) permeability equations respectively.3. The roles of aa and aia in the control of apical sodium entry were studied. 4. Pa increased linearly with log decrease in aOa between 79 and 0-01 mM.

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Influence of vasopressin and amiloride on shunt pathways of frog skin

Cited by 23 publications

References 0 publications

Effects of antidiuretic hormone upon electrical potential and resistance of apical and basolateral membranes of frog skin

Effects of antidiuretic hormone upon electrical potential and resistance of apical and basolateral membranes of frog skin

The electrophysiology of rabbit descending colon

Sodium‐selective micro‐electrode study of apical permeability in frog skin: effects of sodium, amiloride and ouabain.

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