Metabolic studies on frog skin epithelium

Skjelkvale, Leif; Nieder, Virginia K.; Huf, Ernst G.

doi:10.1002/jcp.1030560107

Cited by 18 publications

(6 citation statements)

References 18 publications

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“…Iodoacetate 10-4M produces an inhibition of 17 ~o. This agrees with the evidence that both the glucolytic pathway and the Krebs cycle are in operation in the epithelium of the frog skin (Huf, Doss & Wills, 1957;Skjelkvale, Nieder & Huf, 1960;Curran & Cereijido, 1965). It also agrees with the observation that the inhibition of a single metabolic pathway does not supress completely the transepithelial transport of Na (Leaf & Renshaw, 1957).…”

Section: Part IIsupporting

confidence: 88%

Ionic fluxes in isolated epithelial cells of the abdominal skin of the frogLeptodactylus ocellatus

1975

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Unidirectional ion fluxes are measured in cells isolated by a trypsination-dissection method from the epithelium of the frog Leptodactylus ocellatus. Potassium seems to be contained in a single cellular compartment. The influx of potassium is 0.0068 mumole min-1 mg-1 of dry weight and is carried by a ouabain-sensitive pump. Sodium seems to be contained in two cellular compartments, one of which does not exchange its Na within the experimental period. The possibility that these compartments reflect the existence of different types of cells is not discarded. 49% of the rate constant for the Na efflux is ouabain-sensitive and 23% is ethacrynic-sensitive. Under control conditions the permeability to potassium (PK), sodium (PNa) and chloride (PC1) are 7.6 X 10(-5), 2.6 X 10(-5) and 2.8 X 10(-5) liters/min mg, respectively. The value of PNa is much higher than predicted by current electrical models of the epithelium. The discrepancy might offer some insight into the nature of the "inner facing barrier" of the skin.

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Section: Part IIsupporting

confidence: 88%

Ionic fluxes in isolated epithelial cells of the abdominal skin of the frogLeptodactylus ocellatus

1975

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“…9. It 7 The present experiments cannot rule out absolutely the possibility that a very small K compartment with rapid turnover is involved in a Na-K exchange. However, the presence of such a compartment should lead to altered characteristics of K uptake in the first 1 to 2 minutes when Na flux is altered.…”

Section: Io127mentioning

confidence: 54%

“…3 The average value of D/h 2 for the connective tissue was estimated by direct measurement. The epithelium was removed from the skin by scraping after soaking the tissue for 2 to 3 hours in 4 mM NaHCO (7,8). The connective tissue was mounted in a small chamber (3.14 cm2) and allowed to equilibrate for 1 hour in Ringer's solution.…”

Section: Equationmentioning

confidence: 99%

K Fluxes in Frog Skin

Curran

Cereijido

1965

The Journal of General Physiology

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A method has been developed for measuring K influx into the epithelial cells of frog skin from the inside solution. Diffusion delay in the connective tissue has been taken into account. Ninety-four per cent of skin K was found to exchange with K42 in the inside solution with a single time constant. K influx showed saturation with increasing K concentration, was not altered by imposing a potential difference of -200 mv across the skin, and was inhibited by dinitrophenol, fluoroacetate, and ouabain. Relatively low concentrations of dinitrophenol (5 X 10-' M) and fluoroacetate (10-3 M) had no effect on K influx but caused a 40 per cent decrease in net Na flux. There was no correlation between the rate of K uptake at the "inner barrier" and the rate of net Na transport. Reduction of net Na transport by lowering Na concentration in the outside solution caused little change in K uptake. These observations indicate that there is not a significant Na-K exchange involved in active transport of Na across the skin. K influx was found, however, to require Na in the inside bathing solution.Changes in K concentration of the solutions bathing isolated frog skin are known to affect both transport processes and electric phenomena. Thus, the rate of active Na transport across the skin, measured by short-circuit current, is altered by addition (1) or removal (2, 3) of K from the solution bathing the inner side of the skin, and the potential difference across the skin is strongly dependent on K concentration in the inside solution, particularly in the presence of the impermeant S0 4 anion (4). In 1958 Koefoed-Johnsen and Ussing (4) suggested a model of the skin which included an active transport system involving a forced Na-K exchange system at the inward facing membrane of the transporting cells. The evidence in favor of such an exchange was limited mainly to the observation that Na transport was inhibited by removal of K. Recently, Essig and Leaf (5) have obtained data suggesting that a similar observation in toad bladder cannot be ascribed to a Na-K exchange system. It seemed worthwhile, therefore, to obtain more information regarding the role of K in transport processes in the frog skin by studying the unidirectional K flux from the inside solution into the skin and the influence of various agents upon it.

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“…‫-‬inulin was placed in the inside solution for 1 to 1.5 hr, a mean inulin space of 52% of total tissue water was obtained. In 3 experiments utilizing connective tissue from which the epithelium was removed(11), approximately 70% of the connective tissue water had equilibrated with inulin in this same time interval. Thus total connective tissue water would comprise about 75% and epithelial water 25% of total skin water.…”

mentioning

confidence: 99%

Na Transport across Frog Skin at Low External Na Concentrations

Biber

Chez

Curran

1966

The Journal of General Physiology

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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 Na 22 and Na 24 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 CI. 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.The active transport of Na across isolated frog skin has been examined extensively, but in the majority of studies the outer surface of the skin has been bathed with solutions containing relatively high (115 mM) concentrations of Na. Variation in rates of Na transport and in electrical properties of the skin with changes in Na concentration has also been studied, but in most cases constant anion concentration was maintained by using other cations to substitute for Na. However, the early data of Krogh (1) indicated that intact frogs could take up Na through the skin from solutions containing only 10 6 ‫--‬ M NaCl. Since the model of the Na transport system proposed by Koefoed-Johnsen and Ussing (2) suggests that Na entry into the skin cells is a 1161 on May 12, 2018 jgp.rupress.org Downloaded from

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Metabolic studies on frog skin epithelium

Cited by 18 publications

References 18 publications

Ionic fluxes in isolated epithelial cells of the abdominal skin of the frogLeptodactylus ocellatus

Ionic fluxes in isolated epithelial cells of the abdominal skin of the frogLeptodactylus ocellatus

K Fluxes in Frog Skin

Na Transport across Frog Skin at Low External Na Concentrations

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