| Abstract: | Fractional reabsorption of 4 anions was measured in anesthetized dogs either during inhibition of bicarbonate-dependent intercellular NaCl transport by acetazolamide or man-nitol, 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, CI 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 CI 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, CI 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. |
