Loss of anionic sites from the glomerular basement membrane in human glomerulonephritides

Changes in glomerular anionic sites were analyzed in 31 patients with various types of glomerulonephritis using the high-iron diamine-thiocarbohydrazide-silver proteinate method. On the basis of the degree of proteinuria at the time of biopsy, the patients were divided into 3 groups as follows: Group 1, less than 10 mg/kg/24 h; Group 2, 10-50 mg/kg/24 h; Group 3, more than 50 mg/kg/24 h. The number of glomerular anionic sites per 300 nm length of the lamina rare externa was 16.20 +/- 3.37 in Group 1, 12.19 +/- 3.42 in Group 2 and 9.97 +/- 2.51 in Group 3. Moreover, smaller and irregularly distributed anionic sites, and a greater loss of anionic sites in the paramesangial region were observed in Groups 2 and 3. On the other hand, there was no significant correlation between the mesangial sclerosis index and the number of anionic sites (r = -0.40) in patients with IgA nephropathy (9 cases) and nephritis of Henoch-Schönlein purpura (6 cases). These results suggest that the proteinuria seen in various types of glomerulonephritis is related to the loss of glomerular anionic sites, i.e., dysfunction of the charge-selective barrier.