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Biomedical subjects

W Nagel

Publications and source records attributed to W Nagel.

At least 127 records · Page 7Linked to original sources
PubMed1977

Influence of lithium upon the intracellular potential of frog skin epithelium.

The effect of Li upon the intracellular potential of frog skin (Rana esculenta) was investigated. In the range between 1 and 25 mM Li in the epithelial bathing solution, a semilogarithmic linear relationship between [Li] and intracellular potential under short circuit conditions was obtained. The intracellular potential at all [Li] is quantitatively sufficient to explain the previously reported accumulation of Li in the intracellular space of the frog skin epithelium (Leblanc, G. 1972. Pfluegers Arch. 337:1) on the basis of a passibe entrance step at the outer border. A reduction of the intracellular potential by Li is also observed in the presence of 6 mM Na in the epithelial bathing solution. Consequences regarding the mechanism of uptake of Na across the outer border of the frog skin are discussed.

Amiloride↗
PubMed1977

The dependence of the electrical potentials across the membranes of the frog skin upon the concentration of sodium in the mucosal solution.

1. The dependency of the transmembranal potential differences upon the [Na] of the mucosal bathing solution was investigated in frog skin. Semilogarithmic linear correlations were obtained between [na]0 and the transepithelial potential difference (slope: 28-4 +/- 1-8 mV/dec [Na]0), the potential differences across the outer and the inner membrane under open circuit conditions (slope: 33-4 +/- 1-8 and 4-8 +/- 1-5 mV/dec [Na]0, respectively) and the intracellular potential under short circuit conditions (slope: 33-3 +/- 3-4 mV/dec [Na]0). 2. No difference could be observed between skins incubated in Cl- or SO4-Ringer. 3. The results are not in accordance with the Koefoed-Johnsen & Ussing hypothesis. Neither the polarity of the postulated Na electrode at the outer border could be obtained nor the expected slope of the dependency between potential gradient and [Na] of the mucosal bathing solution. 4. Current recirculation through paracellular shunt pathways is suggested to explain the deviation, at least in part. In addition, the I-R-drop resulting from Na entry across the outer border might account for part of the changes of potential gradients. 5. Under all conditions, Na uptake occurs energetically downhill, but permeability changes of the outer border must be postulated to explain the observed dependency of net Na transport upon [Na]0.

Animals↗
PubMed1976

The intracellular electrical potential profile of the frog skin epithelium.

The potential profile of the frog skin epithelium incubated in Cl-Ringer was reinvestigated with improved technique. Under open circuit conditions (PDtr up to 120 mV) the potential profile was demonstrated to be trough like in contrast to the stair-step like potential profile reported by previous investigators which has probably been recorded after injuring of the punctured cells. In 67 successful impalements the potential difference across the basolateral membranes was 108 +/- 2 mV. The potential across the outer, epithelial-facing membrane was inversely related to the transepithelial PD, but was found to be negative (with respect to the epithelial bathing solution) in all punctures. Electrogenic sodium transport might be responsible for part of the potential difference across the basolateral membranes which correlatee directly with the short circuited state was -73 +/- i mV and decreased with increasing short cirucit current. It is suggested that these changes result from variations of the outer membrane sodium conductance.

Animals↗
PubMed1975

Influx and efflux of sodium at the outer surface of frog skin.

The unidirectional Na influx j12, and Na efflux, j12, at the epithelial surface of the frog skin were determined under various experimental conditions. The j21 was taken as the difference between j12 and the simultaneously measured shortcircuit current (SCC). Errors in j12 determination originating from various transport rates within the skin were kept to a minimum using a normalization procedure. Under control conditions, j12 (1.20 muEquiv/cm-2. hr) was found to be only slightly larger than the SCC (1.10 MUEquiv/cm-2. hr). After inhibition of the transepithelial Na transport by amiloride, ouabain, low temperature and low Na concentration, the reduction of j12 and SCC was almost identical, indicating that the entrance of Na into the epithelium is rate limiting for the transepithelial transport. Compared to the control, j21 remained unchanged after amiloride and ouabain, but was insignificantly reduced at low temperature and significantly reduced at low Na concentration. These data are consistent with the assumption that the Na efflux follows mainly an extracellular pathway.

Amiloride↗