Reevaluation of glomerular charge selective protein-sieving function.

Recently, disorders of the slit diaphragm have been considered as major causes of proteinuria in renal disease and the charge barrier function of the glomerular capillary wall has been given less attention. We evaluated the charge selectivity index (CSI) in 40 patients with podocyte disease (PD), 75 with chronic glomerulonephritis (CGN), and 8 with Dent disease, to reexamine the charge barrier function. We evaluated CSI in Dent disease because the urinary protein profile in Dent disease was assumed to be a concentrate of a normal glomerular filtrate. CSI was defined as the renal clearance ratio between IgA and IgG. CSI values (mean +/- SD) in the CGN and PD groups and in Dent disease were 1.12 +/- 0.25, 0.42 +/- 0.31, and 0.16 +/- 0.06, respectively, suggesting that the charge barrier function was defective in the CGN group and of reduced capacity in the PD group. The results suggest that functional interactions between the slit diaphragm and the glomerular basement membrane exist, and that a slit diaphragm disorder is accompanied by a decrease in the charge barrier function in PD, as argued by the conventional hypothesis.