Permeability parameters of the toad isolatedstratum corneum

Abstract

A technique for isolating the stratum corneum from the subjacent layers of the epithelium was developed which permits studying the stratum corneum as an isolated membrane mounted between half-chambers. The method basically consists of an osmotic shock induced by immersing a piece of skin in distilled water at 50 degrees C for 2 min. When the membrane is bathed on each surface by NaCl-Ringer's solution, its electrical resistance is 14.1 +/- 1.3 omega cm2 (n=10). This value is about 1/100 of the whole skin resistance in the presence of the same solution. The hydraulic filtration coefficient (Lp) measured by a hydrostatic pressure method, with identical solutions on each side of the membrane, is 8.8 X 10(-5) +/- 1.5 X 10(-5) cm sec-1 atm-1 (n=10) in distilled water and 9.2 X 10(-5) +/- 1.4 X 10(-5) cm sec-1 atm-1 (n=10) in NaCl-Ringer's solution. These values are not statistically different and are within the range of 1/80 to 1/120 of the whole skin Lp. The stratum corneum shows an amphoteric character when studied by KCl diffusion potentials at different pH'S. The membrane presents an isoelectric pH of 4.6 +/- 0.3 (n=10). Above the isoelectric pH the potassium transport number is higher than the chloride transport number; below it, the reverse situation is valid. Divalent cations (Ca++ or Cu++) reduce membrane ionic discrimination when the membrane is negatively charged and are ineffective when the membrane fixed charges are protonated at low pH.

Biological and artificial ion exchangers: Electrical measurements with glass microelectrodes

“…Thus, the potential can be assumed to be composed of two phase boundary potentials (Donnan potentials), one at the external solution-matrix interface and the other at the microelectrode solution-matrix interface, and of a diffusion potential between the two interfaces. [10] tentatively interpreted the results on the basis of the diffusion component alone due to its relatively low ion permselectivity, which is controlled by the matrix degree of protonation. [10] tentatively interpreted the results on the basis of the diffusion component alone due to its relatively low ion permselectivity, which is controlled by the matrix degree of protonation.…”

“…In the first group of experiments, toad skins were used. Changes in A(A7 j) polarity with pH were related to alterations of K § and C1transference numbers within the stratum corneum, due to changes in the degree of protonation of the matrix of this structure [10,15]. After a stable electrical potential difference was attained, the external solution was substituted by 0.01 M KC1.…”