Edge damage effect on measurements of urea and sodium flux in frog skin

Helman, S. I.; Miller, DA

doi:10.1152/ajplegacy.1974.226.5.1198

Cited by 33 publications

(7 citation statements)

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“…As shown in Fig with lower theophylline concentrations and also with vasopressin (ADH); the latter, at a dose of 20 mU/ml produces a stimulation (maximal) of 28 4-5% in both Na and urea fluxes, similar to that observed by Helman and Miller (15). The linearity between Na and urea outfluxes is also maintained with vasopressin.…”

Section: Quantitative Relationships Among Na If CL and Urea Fluxessupporting

confidence: 82%

Actions of external hypertonic urea, ADH, and theophylline on transcellular and extracellular solute permeabilities in frog skin.

Lj¹

1975

The Journal of General Physiology

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Increases in transepithelial solute permeability were elicited in the frog skin with external hypertonic urea, theophylline, and vasopressin (ADH). In external hypertonic urea, which is known to increase the permeability of the extracellular (paracellular) pathway, the unidirectional transepithelial fluxes of Na (passive), K, C1, and urea increased substantially while preserving a linear relationship to each other. The same linear relationship was also observed for the passive Na and urea fluxes in regular Ringer and under stimulation with ADH or I0 mM theophylline, indicating that their permeation pathway was extracellular. A linear relationship between C1 and urea fluxes could be demonstrated if the skins were separated according to their open circuit potentials; parallel lines were obtained with increasing intercepts on the CI axis as the open circuit potential decreased. The slopes of the C1 vs. urea lines were not different from that obtained in external hypertonic urea, indicating that this relationship described the extracellular movement of C1. The intercept on the ordinate was interpreted as the contribution from the transcellular CI movement. In the presence of 0.5 mM theophylline or 20 mU/ml of ADH, mainly the transcellular movement of CI increased, whereas 10 mM theophylline caused increases in both transcellular and extracellular C1 fluxes. These and other data were interpreted in terms of a possible intracellular control of the theophylline-induced increase in extracellular fluxes. The changes in passive solute permeability were shown to be independent of active transport. The responses of the active transport system, the transcellular and paracellular pathways to theophylline and ADH could be explained in terms of the different resulting concentrations of cyclic 5 t .Y-AMP produced by each of these substances in the tissue.

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Section: Quantitative Relationships Among Na If CL and Urea Fluxessupporting

confidence: 82%

Actions of external hypertonic urea, ADH, and theophylline on transcellular and extracellular solute permeabilities in frog skin.

Lj¹

1975

The Journal of General Physiology

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“…However, the permeability of the tissue under investigation is affected by the compression exerted at its edge by clamping and this effect has been referred to as edge damage. For example, in frog skin the edge damage caused the measured values of permeability to urea and sodium to increase by 7- and 20.8 fold above their nonedge-damaged values [22]. For this reason, we have used an alternative simple apparatus, minimizing the edge effect (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

Why Amphibians Are More Sensitive than Mammals to Xenobiotics

et al. 2009

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Dramatic declines in amphibian populations have been described all over the world since the 1980s. The evidence that the sensitivity to environmental threats is greater in amphibians than in mammals has been generally linked to the observation that amphibians are characterized by a rather permeable skin. Nevertheless, a numerical comparison of data of percutaneous (through the skin) passage between amphibians and mammals is lacking. Therefore, in this investigation we have measured the percutaneous passage of two test molecules (mannitol and antipyrine) and three heavily used herbicides (atrazine, paraquat and glyphosate) in the skin of the frog Rana esculenta (amphibians) and of the pig ear (mammals), by using the same experimental protocol and a simple apparatus which minimizes the edge effect, occurring when the tissue is clamped in the usually used experimental device.The percutaneous passage (P) of each substance is much greater in frog than in pig. LogP is linearly related to logKow (logarithm of the octanol-water partition coefficient). The measured P value of atrazine was about 134 times larger than that of glyphosate in frog skin, but only 12 times in pig ear skin. The FoD value (Pfrog/Ppig) was 302 for atrazine, 120 for antipyrine, 66 for mannitol, 29 for paraquat, and 26 for glyphosate.The differences in structure and composition of the skin between amphibians and mammals are discussed.

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“…This shunt causes significant reduction of the measured electrical potential and resistance (Dobson & Kidder, 1968;Helman & Miller, 1973). Helman and Miller (1974) found that the values of the permeability of urea, the passive permeability of sodium, and the electromotive force of the sodium battery (ENa) are strongly dependent on the extent of the edge damage. On the basis of their observation, we evaluated, in the present study, the extent of the edge damage by measuring these parameters.…”

Section: Resultsmentioning

confidence: 99%

Studies on chloride permeability of the skin ofLeptodactylus ocellatus: I. Na+ and Cl− effect on passive movements of Cl−

1978

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The outflux of chloride through the isolated skin (JCl31) of the South American frog Leptodactylus ocellatus (L.) is carried by a mechanism that saturates at high concentration of chloride on the inside, and is stimulated by the presence of Cl- in the outer solution (trans side). The presence of Na+ on the outside, by itself, does not increase JCl31. However, when JCl31 is already increased by chloride on the trans side, the addition of Na+ produces a significant further increase. At low concentration of Cl- on the outside JCl31 is carried by an exchange diffusion mechanism. At high concentrations of Cl- outside, JCl31 proceeds through a route which involves changes in electrical parameters. The results suggest that both mechanisms are located on the cell membranes and, therefore, that the fluxes would cross through the cytoplasm of the cells. Na+ stimulates the second mechanism only.

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Edge damage effect on measurements of urea and sodium flux in frog skin

Cited by 33 publications

References 0 publications

Actions of external hypertonic urea, ADH, and theophylline on transcellular and extracellular solute permeabilities in frog skin.

Actions of external hypertonic urea, ADH, and theophylline on transcellular and extracellular solute permeabilities in frog skin.

Why Amphibians Are More Sensitive than Mammals to Xenobiotics

Studies on chloride permeability of the skin ofLeptodactylus ocellatus: I. Na+ and Cl− effect on passive movements of Cl−

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