Coupled transepithelial sodium and potassium transport across isolated frog skin: effect of ouabain, amiloride and the polyene antibiotic filipin.
Addition of the polyene antibiotic filipin (50 microM) to the outside bathing solution (OBS) of the isolated frog skin resulted in a highly significant active outward transport of K+ because filipin per se increases the nonspecific Na+ and K+ permeability of the outward facing membrane. The K+ transport was calculated from the chemically determined changes in K+ concentrations in the solution bathing the two sides of the skin. The active transepithelial K+ transport required the presence of Na+ in the OBS, but not in the inside bathing solution (IBS), and it was inhibited by the Na+, K+-ATPase inhibitor ouabain. The addition of Ba++ to the IBS in the presence of filipin in the OBS resulted in an activation of the transepithelial K+ transport and in an inhibition of the active Na+ transport. This is in agreement with the notion that Ba++ decreases the passive K+ permeability of the inward facing membrane. In the presence of amiloride (which blocks the specific Na permeability of the outward facing membrane) and Ba++ there was a good correlation between the active Na+ and K+ transport. It is concluded that the active transepithelial K+ transport is carried out by a coupled electrogenic Na-K pump, and it is suggested that the pump ratio (Na/K) is 1.5.
D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D001001:Anura; D001464:Barium / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D002463:Cell Membrane Permeability; D004848:Epithelium / Q000378:metabolism; D005260:Female; D005372:Filipin / Q000494:pharmacology*; D008297:Male; D008954:Models, Biological; D010042:Ouabain / Q000494:pharmacology*; D011090:Polyenes / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism*; D011719:Pyrazines / Q000494:pharmacology*; D011896:Rana temporaria; D012867:Skin / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*
D011090:Polyenes; D011719:Pyrazines; D001464:Barium; D010042:Ouabain; D000584:Amiloride; D005372:Filipin; D012964:Sodium; D011188:Potassium