A simple method to detect an albumin permeability factor in the idiopathicnephrotic syndrome

Background Several investigators have detected an albumin permeability fact or in the serum of patients with the idiopathic nephrotic syndrome (INS), t hat is, minimal change disease (MCD) or focal segmental glomerulosclerosis (FSGS), but the methods used have been complex. Methods. We describe here a simpler method using cultured rat glomerular ep ithelial cell monolayers grown to confluence on Millicell filters, which al low sampling of apical and basolateral media,I-125-labeled human serum albu min (I-125-HSA) was added to the basolateral compartment, and its leakage a cross the epithelial cell monolayer into the apical compartment was measure d. Results. In untreated cells (negative control), the albumin Leakage reached 5.3% at 18 hours. Cell monolayers fixed with 95% ethanol (positive control ) showed 62% leakage. Sera from three out of four patients with MCD and thr ee out of four with FSGS resulted in considerable albumin leakage, whereas sera from nine patients with other types of nephrotic renal disease and fiv e normal subjects caused no leakage. Conclusion. This study shows that the Millicell system provides a simple an d useful method to screen for permeability Factors in the INS.