Effect of unreabsorbed anions on proximal and distal transtubular potentials in rats

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Abstract
Proximal and distal transtubular potential differences (ET) were measured in Na-fed and Na-depleted rats given infusions of 5% glucose in water, 0.9 m NaCl, 0.5 m NaHCO3, 0.5 m Na2SO4, and 0.25 m Na4Fe(CN)6. Proximal ET was –23.8 ± 0.8 mv and was uninfluenced by intravenous infusions of various Na+ salts. Distal ET was –53.8 ± 1.9 mv and rose sharply with infusions of Na+ salts of nonreabsorbable anions; the maximum rise was –31 mv in salt-depleted rats given Na2SO4. The rise in distal ET associated with polyvalent anions was attributed to both higher cation concentrations and lower Cl– concentrations in distal tubular fluid produced by infusions of these salts. It was suggested that the rise in distal ET is responsible for the known augmentation of K+ and H+ excretion produced by these salts.