Minimal change nephropathy: an electrochemical disorder of the glomerular membrane.

To investigate the mechanism of proteinuria in minimal change nephropathy, the renal handling of dextrans was studied in seven nephrotic patients with this disorder. Although the urinary excretion of albumin was greatly increased, the urinary excretion and fractional clearance of dextrans (Einstein-Stokes radius (ESR), range 20 to 48 A) were depressed relative to those in nonproteinuric healthy volunteers. This suggests that mean glomerular pore size or pore density was reduced. Uptake of colloidal iron by glomeruli obtained from these patients by needle biopsy was diminished, suggesting loss of glomerular polyanion. Since the fractional clearance of dextrans similar in size to albumin was depressed, not increased, it is proposed that the lack of electrostatic interaction between the glomerular capillaries and polyanionic plasma albumin (ESR = 36 A) accounts for the selective albuminuria which characterizes minimal change nephropathy.