The state of water in the outer barrier of the isolated frog skin

Grigera, J. Raúl; Cereijido, Marcelino

doi:10.1007/bf02431967

Cited by 15 publications

(3 citation statements)

References 31 publications

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“…This issue was not tested rigorously in the present experiments , since, for the reasons indicated previously, permeation coefficients were measured only at two temperatures. However, a similar assumption has been made by Hays et al [-22] in evaluating the effect of ADH on the EA for water diffusion in toad urinary bladder; and, both in frog skin [18] and in rabbit gall bladder [51], water permeation appears to follow a linear Arrhenius relationship for the temperature range 21-39 ~ Given this caveat, Tables 2 and 3 summarize the results for simultaneous measurements of the apparent activation energies for water and n-butyr- amide permeation. In the absence of ADH (Table 2), E A was 9.35_+0.92 and 19.40 _+ 1.6 kcal per mole for, respectively, Py and n-butyramide permeation; the mean paired difference between these two values was 7.7 + 0.74 (P < 0.002).…”

Section: Apparent Activation Energies For Water and Solute Permeationmentioning

confidence: 62%

Effect of antidiuretic hormone on water and solute permeation, and the activation energies for these processes, in mammalian cortical collecting tubules

et al. 1977

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Summary. The present studies were designed to assess the ways in which antidiuretic hormone (ADH) alters water and solute permeation across isolated, rabbit cortical collecting tubules. In earlier work, it was observed: that ADH produced a tenfold increment in P/(cm per sec), the osmotic water permeability coefficient, and a fourfold increment in PD~ (cm per sec), the diffusional water permeability coefficient; that small hydrophilic solutes such as urea, thiourea and acetamide (each having oil/water partition coefficients __< 0.0008) had vanishingly low permeation coefficients and unity reflection coefficients, even in the presence of ADH; that lumen to bath osmosis involved a transcellular route; and, that the disparity between Ps and Po~, either with or without ADH, could be rationalized in terms of cellular diffusion constraints, i.e., that water transport across luminal membranes was diffusionat.The present experiments evaluated the effects of ADH on diffusion of moderately lipophilic solutes (e.g., butyramide, isobutyramide, and antipyrine, each solute having an oil/water partition > 0.0008) across luminal membranes of rabbit cortical collecting tubules, and the effects of ADH on the apparent activation energies (EA, kcal per mole) for water and solute permeation across these tubules. Three major results were obtained: (1) ADH produced a 60-100 ~ increase in the permeation rates for these solutes. (2) The ADH-dependent apparent E A for water permeation was 9.35_+0.92 kcal per mole, and the ADH-dependent apparent E A for permeation of moderately lipophilic solutes was in the range 15.8-19.6 kcal per mole. (3) The ADH-independent E A values for these transport processes were statistically indistinguishable from the ADH-dependent E A values.When viewed in the context of transport mechanisms for water and solute permeation across synthetic lipid bilayer membrane systems, these results are consistent with the possibility that diffusion of water and moderately lipophilic solutes across mammalian collecting tubules may involve parallel sites in luminal plasma membranes: routes for water diffusion

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Section: Apparent Activation Energies For Water and Solute Permeationmentioning

confidence: 62%

Effect of antidiuretic hormone on water and solute permeation, and the activation energies for these processes, in mammalian cortical collecting tubules

et al. 1977

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“…In preliminary experiments we noticed that, provided it is ice cold, the washing with isotonic sucrose might be continued for at least 9 sec, without changing the slope of the uptake curve. This is expectable as it was observed that the flux of water (Grigera & Cereijido, 1971) and sodium (Rodriguez Boulfin, Moreno, Rotunno & Cereijido, 1972, unpublished) (j~o and J~2 A) have a high activation energy.…”

Section: The Flux Of Sodium Across the Outer Border Of The Epitheliummentioning

confidence: 66%

Barriers to sodium movement across frog skin

et al. 1973

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Summary. The aim of this paper is to obtain information on the number, nature and location of the barriers to Na movement across the frog skin, and on the size and location of the Na-pool that might be contained between these barriers. On the basis that Na penetrates passively across an outer barrier, and is actively extruded across an inner barrier which is impermeable to passive movements of Na, we expected to detect at least the Na-pool of a single cell layer containing some 10 -8 moles per cm 2 of epithelium (i.e., in a cell layer 5 g thick and with 21 mM Na). Yet no Na-pool with these characteristics was found. The method employed could have detected a Na-pool at least an order of magnitude smaller than the one expected. It is concluded that either a Na-pool does not exist (except for the Na bound to the mechanisms operating the translocation), or else that the Na-pool is contained between barriers with different characteristics than the ones assumed above. In the first case, Na transport across the epithelium would consist of a translocation across a single asymmetrical functional "barrier". In the second case, the experimental results would require that ouabain either directly (by inhibiting an active step) or indirectly (through a mediated decrease of the Na permeability of the outer barrier) prevents Na penetration at the outer border.

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“…Both values were well above the 4.6 kcal/mole reported THE JOURNAL OF GENERAL PHYSIOLOGY VOLUME 59, 1972 ' pages 519-533 by Wang et al (16) for diffusion of water in bulk solution. Such high activation energies have been explained (4)(5)(6)(7) as resulting from the extensive bonding of water with the components of the aqueous channel or from the formation of icelike structures by water within the membrane. It is not possible on the basis of the diffusion data alone to determine whether the movement of individual water molecules is primarly restrained by water-water or by water-membrane hydrogen bonding.…”

Section: Introductionmentioning

confidence: 99%

Temperature Dependence of Vasopressin Action on the Toad Bladder

Eggena

1972

The Journal of General Physiology

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Toad bladders were challenged with vasopressin at one temperature, fixed on the mucosa with 1% glutaraldehyde, and then subjected to an osmotic gradient at another temperature. Thus, the temperature dependence of vasopressin action on membrane permeability was distinguished from the temperature dependence of osmotic water flux. As the temperature was raised from 200 to 38 0 C, there was a substantial increase in the velocity of vasopressin action, but osmotic flux was hardly affected. In this range of temperature the apparent energy of activation for net water movement across the bladder amounted to only 1.2 kcal/mole, a value well below the activation energy for bulk water viscosity. It is suggested that osmotic water flux takes place through narrow, nonpolar channels in the membrane. When the temperature was raised from 40 to 20 0 C, both vasopressin action as well as osmotic water flux were markedly enhanced. Activation energies for net water movement were now 8.5 kcal/mole (4°-9C) and 4.1 kcal/mole (9 0 -20 0 C), indicating that the components of the aqueous channel undergo conformational changes as the temperature is lowered from 20 0 C. At 43°C bladder reactivity to vasopressin was lost, and irreversible changes in selective permeability were observed. The apparent energy of activation for net water movement across the denatured membrane was 6.6 kcal/mole. Approximately 1 puosmol of NaCl was exchanged for 1 1 of H 2 0 across the denatured membrane.

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The state of water in the outer barrier of the isolated frog skin

Cited by 15 publications

References 31 publications

Effect of antidiuretic hormone on water and solute permeation, and the activation energies for these processes, in mammalian cortical collecting tubules

Effect of antidiuretic hormone on water and solute permeation, and the activation energies for these processes, in mammalian cortical collecting tubules

Barriers to sodium movement across frog skin

Temperature Dependence of Vasopressin Action on the Toad Bladder

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