Permeability parameters of the toad isolated stratum corneum.
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.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002024:Bufo marinus; D002413:Cations, Divalent; D004058:Diffusion; D004553:Electric Conductivity; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D010539:Permeability; D011189:Potassium Chloride / Q000378:metabolism; D012867:Skin / Q000166:cytology / Q000378:metabolism; D012879:Skin Physiological Phenomena; D014867:Water / Q000378:metabolism
D002413:Cations, Divalent; D014867:Water; D011189:Potassium Chloride