Effect of plasma albumin on sodium reabsorption in patients with nephrotic syndrome

Effect of plasma albumin on sodium reabsorption in patients with nephrotic syndrome.The effects of plasma albumin on renal tubular sodium reabsorption were studied in patients with the nephrotic syndrome who had severe hypoalbuminemia and edema.The technique of distal tubular blockade by chlorothiazide and ethacrynic acid with replacement of urinary losses was used to assess sodium reabsorption.“Proximal” tubular fractional reabsorption was distinctly lower than has been reported in normal individuals and in patients with cirrhosis and ascites studied under similar conditions.This finding suggests that hypoalbuminemia in man decreases fractional sodium reabsorption in the proximal tubules as has been demonstrated in laboratory animals.This conclusion was strengthened by demonstrating increased fractional and absolute sodium reabsorption when concentrated albumin was infused in the presence of the diuretic agents.Volume expansion with an iso-oncotic electrolyte solution resulted in a further decrease in “proximal” tubular fractional sodium reabsorption, usually in association with increased GFR.The data suggest that sodium retention and edema formation in patients with the nephrotic syndrome and hypoalbuminemia occurs despite depressed proximal tubular fractional reabsorption and therefore may involve reabsorption of an excessively large fraction of filtered sodium in distal portions of the nephron, primarily at sites where ethacrynic acid blocks sodium reabsorption