Effect of transepithelial concentration gradients on the passive fluxes of sodium across toad bladder

Chen, Jing S.; Walser, Mackenzie

doi:10.1007/bf01869147

Cited by 4 publications

(23 citation statements)

References 7 publications

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“…In recent studies of electrolyte permeation of toad bladder, we have observed that the effects of gradients of electrical potential [4-], concentration [5], or both [6] on unidirectional and net fluxes of ions conform closely to the predictions of a model based on a constant ratio of bulk permeability coefficient to tracer permeability coefficient. This ratio is the same as the ratio of bulk diffusion coefficient to '~ tradiffusion coefficient", as defined by Albright and Mills [1-].…”

mentioning

confidence: 52%

“…Bladder sacs of Dominican toads (Bufo marinus) were prepared and mounted as previously described [4][5][6].…”

Section: Methodsmentioning

confidence: 99%

“…We postulate, as before [5,6], that this integrated equation is valid even if the concentration gradient is not linear, and that concentrations in the bulk media bathing the membrane can be substituted for concentrations within the membrane in the integrated equation.…”

Section: Theoreticalmentioning

confidence: 98%

“…By extension from the theoretical formulation of Meares and Sutton [21], we have shown [5,6] mathematically and experimentally that in the presence of an electrochemical potential gradient of a solute, in general,…”

Section: Theoreticalmentioning

confidence: 99%

“…where R, T, % ~, x, and d/O are as previously defined [4][5][6], U i is ionic mobility, and u o is the velocity of the solvent in a given frame of a reference. Therefore, the net flux of a nonelectrolyte, J, may be written in general as…”

Section: Theoreticalmentioning

confidence: 99%

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Concentrationo-dependence of nonelectrolyte permeability of toad bladder

Chen

Walser

1979

J. Membrain Biol.

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A theoretical formulation was derived for the dependence of bulk solute permeability, P, defined as net flux divided by concentration gradient, delta c, across any membrane in which solute concentration is controlling for net flux, delta J. According to this formulation, delta J is stimulated by increments in trans concentration, c2, in the range c2/c1 equals 0.0--0.1. Net flux of urea across toad bladder down concentration gradients was shown to be stimulated threefold by small increments in trans urea concentration. The theory also predicts that, in the absence of concentration gradients, tracer permeability, P, defined as tracer flux divided by tracer concentration, will be independent of c provided that P equals P, but will diminish with increasing c if P/P less than 1.P/P was not significantly different from unity for urea, and both P and P were independent of c in the absence of concentration gradients. However, P/P was significantly less than unity (0.90 and 0.85) for thiourea and mannitol, respectively. In conformity with theory, P (and also P) of these two solutes, measured as c was increased by 3--4 orders of magnitude, diminished progressively. These effects are more consistent with this formulation than with transport via a saturable carrier.

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mentioning

confidence: 52%

“…Bladder sacs of Dominican toads (Bufo marinus) were prepared and mounted as previously described [4][5][6].…”

Section: Methodsmentioning

confidence: 99%

Section: Theoreticalmentioning

confidence: 98%

Section: Theoreticalmentioning

confidence: 99%

Section: Theoreticalmentioning

confidence: 99%

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Concentrationo-dependence of nonelectrolyte permeability of toad bladder

Chen

Walser

1979

J. Membrain Biol.

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Concentration-dependence of nonelectrolyte permeability of toad bladder

1980

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Pathways for movement of ions and water across toad urinary bladder

Civan

DiBona

1978

J. Membrain Biol.

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Hypertonicity of the mucosal bathing medium increases the electrical conductance of toad urinary bladder by osmotic distension of the epithelial "tight" or limiting junctions. However, toad urine is not normally hypertonic to plasma. In this study, the transmural osmotic gradient was varied strictly within the physiologic range; initially hypotonic mucosal bathing media were made isotonic by addition of a variety of solutes. Mucosal NaCl increased tissue conductance substantially. This phenomenon could not have reflected soley an altered conductance of the transcellular active transport pathway since mucosal KCl also increased tissue conductance, whether or not Na+ was present in the bathing media. The effect of mucosal NaCl could not have been mediated solely by a parallel transepithelial pathway formed by damaged tissue since mucosal addition of certain nonelectrolytes also increased tissue conductance. Finally, the osmotically-induced increase in conductance could not have occurred soley in transcellular transepithelial channels in parallel with the active pathway for Na+, since the permeability to 22Na from serosa to mucosa (s to m) was also increased by mucosal addition of NaCl; a number of lines of evidence suggest that s-to-m movement of Na+ proceeds largely through paracellular transepithelial pathways. The results thus establish that the permeability of the limiting junctions is physiologically dependent on the magnitude of the transmural osmotic gradient. A major role is proposed for this mechanism, serving to conserve the body stores of NaCl from excessive urinary excretion.

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Effect of transepithelial concentration gradients on the passive fluxes of sodium across toad bladder

Cited by 4 publications

References 7 publications

Concentrationo-dependence of nonelectrolyte permeability of toad bladder

Concentrationo-dependence of nonelectrolyte permeability of toad bladder

Concentration-dependence of nonelectrolyte permeability of toad bladder

Pathways for movement of ions and water across toad urinary bladder

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