Mechanism of action PGE2 on active transepithelial Na transport in frog skin

1984 ◽  
Vol 27 ◽  
pp. 81
Author(s):  
S.I. Helman ◽  
T.C. Cox ◽  
W.J. Els ◽  
W. Van Driessche
Keyword(s):  
Mechanism Of Action ◽  
Frog Skin ◽  
Na Transport ◽  
Transepithelial Na Transport

pHi determines rate of sodium transport in frog skin: results of a new method to determine pHi

1994 ◽  
Vol 266 (3) ◽  
pp. F367-F374 ◽  
Author(s):  
R. Rick
Keyword(s):  
Frog Skin ◽  
Nuclear Potential ◽  
Na Channel ◽  
Cytoplasmic Ph ◽  
Na Transport ◽  
Principal Cells ◽  
Weak Organic Acid ◽  
Transepithelial Na Transport ◽  
Cell Layers ◽  
Important Regulator

The pH of the isolated frog skin epithelium was determined on a cellular and subcellular level based on the distribution of a weak organic acid, 4-bromobenzoic acid. The indicator is detectable by X-ray microanalysis due to the presence of an element label. The results show that the pH of principal cells, but not the Na concentration, is closely correlated with the rate of transepithelial Na transport. Acidification leads to an inhibition of Na transport, regardless of whether the change was spontaneous or experimentally induced. Under the conditions of this study, the pH of principal cells was not well regulated. At a bath pH of 7.0, large pH differences between the cell layers were detectable. In mitochondria-rich cells, the pH was a function of the intracellular Cl concentration but not the Na transport rate. The cytoplasmic pH consistently exceeded the nuclear pH. The nuclear-cytoplasmic pH differential in principal cells amounted to 0.3 pH units, which is equivalent to a nuclear potential of -17 mV. The results support the view that the intracellular pH (pHi) is an important regulator of transepithelial Na transport. Regulation is primarily achieved at the level of the apical Na channel, making the Na influx the rate-limiting step in Na reabsorption.

Transepithelial transport kinetics and Na entry in frog skin: effects of novobiocin

1976 ◽  
Vol 231 (6) ◽  
pp. 1866-1874 ◽  
Author(s):  
LJ Cruz ◽  
TU Biber
Keyword(s):  
Kinetic Parameters ◽  
Frog Skin ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Close Correlation ◽  
Transport Kinetics ◽  
Transepithelial Transport ◽  
Linear Component ◽  
Na Transport ◽  
Transepithelial Na Transport

Na+ entry across the outer surface of frog skin and transepithelial Na transport were studied simultaneously at different [Na] in either the presence or absence of novobiocin by direct measurements of J12 (unidirectional uptake) and Io (short-circuit current). J12 consisted of two components: one linear, the other saturable. The kinetic parameters of the saturating components in controls were close to the kinetic parameters of overall transepithelial transport (Jm12 = 1.68+/-0.13 mleq cm-2h-1; Io =1.80+/-0.14 mueq cm-2h-1. K12 = 6.02+/-1.27 mM;Kio=6.12+/-1.33 mM). Novobiocin significantly augmented net transepithelial Na transport by increasing J13. J31 remained unaffected. A 1:1 relationship between the saturating component of J12 and Io was observed in both treated and untreated skins at all [Na] tested. (Jm12Iom, k12, and Kio were significantly larger in treated skins, but despite very drastic changes in transport rates, a close correlation between kinetic parameters of entry step and transepithelial transport was maintained. This suggests that the kinetics of transepithelial transport may simply reflect those of the rate-limiting step: the Na entry across the outer barrier of the skin. The results indicate that the linear component of J12 is not involved in transepithelial transport kinetics.

Effects of standard diuretics and RPH 2823 on transepithelial Na+ transport in isolated frog skin

1986 ◽  
Vol 64 (16) ◽  
pp. 750-759
Author(s):  
J. Kipnowski ◽  
J. Passon ◽  
C. Detjen ◽  
R. Düsing ◽  
S. Miederer ◽  
...  
Keyword(s):  
Frog Skin ◽  
Na Transport ◽  
Transepithelial Na Transport

scholarly journals Ouabain on active transepithelial sodium transport in frog skin: studies with microelectrodes.

1979 ◽  
Vol 74 (1) ◽  
pp. 105-127 ◽  
Author(s):  
S I Helman ◽  
W Nagel ◽  
R S Fisher
Keyword(s):  
Frog Skin ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Equilibrium Potential ◽  
Electrical Model ◽  
Na Transport ◽  
Rapid Phase ◽  
Transepithelial Na Transport ◽  
Transepithelial Voltage ◽  
Transepithelial Sodium Transport

Studies were done with isolated frog skin to determine the effects of 10(-4) M ouabain on the electrophysiological parameters of outer and inner barriers of the Na-transporting cells. Microelectrodes were used to impale the skins from the outer surface to determine the intracellular voltages (Vsco) under conditions of short-circuiting and under conditions where a voltage clamp was used to vary the transepithelial voltage, VT. From this, the electrical resistances of outer (Rfo) and inner (RI) barriers were estimated. In addition, the driving force for active transepithelial Na transport (ENa = E'1) was estimated from the values of VT when the Vo = 0 mV (Helman and Fisher. 1977. J. Gen. Physiol. 69: 571-604). Studies were done with skins bathed with the usual 2.4 meq/liter [K]i in the inner solution as well as with reduced [K]i of 0.5 and 0 meq/liter. Characteristically, the responses to ouabain could be described by an initial rapid phase (5-10 min) during which time the Ri was increased markedly and the E'1 was decreased from control values. Thereafter, during the slow phases of the response, the resistances of both outer and inner barriers increased continuously and markedly with time leading ultimately to essentially complete inhibition of the short-circuit current. Similar studies were done with skins exposed to 10(-4) M amiloride in the outer solution. Although estimates of Ri could not be obtained under these conditions, the effects on the Vsco and E'1 were similar to those observed for the Na-transporting skins. However, the magnitudes of the effects were less and relatively slower than observed for the Na-transporting skins. The results of these studies were analyzed within the context of a proposed electrical model that takes into account the observation that the magnitude of the voltage at the inner barrier appears to exceed the equilibrium potential for K especially when transepithelial Na transport is inhibited at the apical barrier of the cells.

The Sigma-1 Receptor Ligands Chlorpromazine and Trifluoperazine Inhibit Na+ Transport in Frog Skin Epithelium

BIOPHYSICS ◽  
2020 ◽  
Vol 65 (5) ◽  
pp. 784-787
Author(s):  
A. V. Melnitskaya ◽  
Z. I. Krutetskaya ◽  
V. G. Antonov ◽  
N. I. Krutetskaya
Keyword(s):  
Frog Skin ◽  
Receptor Ligands ◽  
Na Transport ◽  
Sigma 1 Receptor ◽  
Skin Epithelium ◽  
Frog Skin Epithelium ◽  
Sigma 1

scholarly journals Blocker-related changes of channel density. Analysis of a three-state model for apical Na channels of frog skin.

1990 ◽  
Vol 95 (4) ◽  
pp. 647-678 ◽  
Author(s):  
S I Helman ◽  
L M Baxendale
Keyword(s):  
Frog Skin ◽  
Noise Analysis ◽  
Kinetic Scheme ◽  
State Model ◽  
Na Channel ◽  
Na Channels ◽  
Na Transport ◽  
Open Probability ◽  
Wide Range ◽  
Three State Model

Blocker-induced noise analysis of apical membrane Na channels of epithelia of frog skin was carried out with the electroneutral blocker (CDPC, 6-chloro-3,5-diamino-pyrazine-2-carboxamide) that permitted determination of the changes of single-channel Na currents and channel densities with minimal inhibition of the macroscopic rates of Na transport (Baxendale, L. M., and S. I. Helman. 1986. Biophys. J. 49:160a). Experiments were designed to resolve changes of channel densities due to mass law action (and hence the kinetic scheme of blocker interaction with the Na channel) and to autoregulation of Na channel densities that occur as a consequence of inhibition of Na transport. Mass law action changes of channel densities conformed to a kinetic scheme of closed, open, and blocked states where blocker interacts predominantly if not solely with open channels. Such behavior was best observed in "pulse" protocol experiments that minimized the time of exposure to blocker and thus minimized the contribution of much longer time constant autoregulatory influences on channel densities. Analysis of data derived from pulse, staircase, and other experimental protocols using both CDPC and amiloride as noise-inducing blockers and interpreted within the context of a three-state model revealed that Na channel open probability in the absence of blocker averaged near 0.5 with a wide range among tissues between 0.1 and 0.9.

Coupling of volume and Na+ transport in frog skin epithelium

1989 ◽  
Vol 66 (1-2) ◽  
pp. 183-190 ◽  
Author(s):  
Cherng-Shing R. Tang ◽  
Kim Peterson-Yantorno ◽  
Mortimer M. Civan
Keyword(s):  
Frog Skin ◽  
Na Transport ◽  
Skin Epithelium ◽  
Frog Skin Epithelium
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