Chloride transport across isolated skin of Rana pipiens

The influx of Cl- across isolated frog skin bathed on the outside by 0.8 mM NaCl is about 100 nmol cm-2 h-1, which is approximately twice the Cl- influx in intact animals. The influx consists of diffusion (1%), exchange diffusion (38%), and active transport (60%). About 80% of the influx is independent of Na+ in the outer bath and is also independent of concomitant inward movement of cations. Chloride is exchanged for anions, probably HCO-3. The Cl- transport system is saturable; Vmax is about 200 nmol cm-2 h-1, and Ks is about 0.7 mM Cl-. High external concentrations of NaCl increase unidirectional fluxes of Cl- and urea, indicating a change in paracellular pathways. Active transport of Cl- is temperature sensitive (Q10 equals 2.68) and is inhibited by cyanide, dinitrophenol, iodoacetic acid, iodide, thiocyanate, and acetazolamide. The Na-independent component of JClin was unaffected by amiloride, ouabain, or eserine, all of which inhibit Na+ transport.