Transcellular and intercellular transport of anions in the kidney tubules of dogs.

Fractional reabsorption of 4 anions was measured in anesthetized dogs either during inhibition of bicarbonate-dependent intercellular NaCl transport by acetazolamide or mannitol, or during inhibition of transcellular NaCl reabsorption in the diluting segment by ethacrynic acid or ouabain. When administered subsequent to ethacrynic acid, acetazolamide reduced fractional reabsorption of SCN, Br, Cl and I by 0.28 +/- 0.03, 0.28 +/- 0.02, 0.27 +/- 0.03 and 0.31 +/- 0.03. Mannitol given after ethacrynic acid reduced fractional reabsorptions by 0.23 +/- 0.04, 0.20 +/- 0.04, 0.20 +/- 0.05 and 0.20 +/- 0.05, respectively. Thus, the bicarbonate-dependent reabsorption system does not discriminate between these anions. Ethacrynic acid reduced fractional reabsorption of SCN, Br and Cl by 0.28 +/- 0.05, 0.24 +/- 0.03, 0.22 +/- 0.03 in one group, by 0.32 /+- 0.04, 0.34 +/- 0.03, 0.31 +/- 0.04 in another group, with significantly smaller reductions for I, 0.07 +/- 0.03, in both groups. Ouabain reduced fractional reabsorption of Br, Cl and I by 0.48 +/- 0.04, 0.46 +/- 0.04 and 0.24 +/- 0.03, respectively. Thus, anion permeability or transport affinity for bromide, chloride and iodide are equal both for inter- and transcellular transport, while iodide transport is slow along the transcellular route. No specific transport mechanism for chloride was detected.