Renal hemodynamics and tubular fractional sodium reabsorption (FSR) were evaluated by clearance techniques during acute and chronic extracellular volume expansion in man. (1 − V/GFR) × 100 was used as an index of proximal and (CH2O/V) × 100 as an estimate of distal fractional reabsorption. After acute loading with isotonic saline 37 ml/kg body wt, proximal FSR decreased by 4.8% and distal FSR decreased by 4.4%. After comparable chronic expansion by mineralocorticoids (“escape”), proximal FSR also decreased by 3.9%, but distal reabsorption was not altered.
Edward A. Alexander, David W. Doner Jr., R. Brewer Auld, Norman G. Levinsky