Abstract

Cyclosporine A(CsA) is known as a potent immunosupressive agent, and recently its supressive effects of proteinuria in minimal change nephrotic syndrome, and other glomerular diseases have been demonstrated. But the mechanism of supression of proteinuria is not clear. This study aimed to investigate the mechanism of supression of proteinuria in puromycin aminonucleoside (PAN) induced minimal change nephrosis(MCN), by a single dose of PAN, and focal segmental glomerulosclerosis(FSG) by long term repeated administration of PAN with unilateral nephrectomy in Sprague-Dawley rats, using transmission electron microscopy. We also analysed the effects of CsA on the histopathologic changes such as glomerular sclerosis, and subtypes of infiltrated mononuclear cells in glomeruli and renal interstitium. The results are as follows: Marked proteinuria was developed in MCN and FSG groups. It was significantly reduced by administration of CsA. BUN and creatinine were significantly increased in FSG with the administration of CsA, compared with FSG without CsA. On ultrastructural examination, MCN group showed effacement of foot processes, and microvillous transformation. Occasional focal detatchment of podocytes from the GBM, vacuolar degeneration, and electron dense droplets in the podocytes were also seen. The latter findings were remarkably reduced by CsA. The Above ultrastructural findings, seen in the MCN group, were more severe in the FSG groups. On comparison of ultrastructural fingings of FSG with or without CsA groups, severe vacuolar degeneration, abundant electron dense granules, and focal detatchment of foot processes were more frequently seen in FSG groups and they were significantly reduced by CsA. But irregularity and thickening of GBM were deepend in FSG with CsA group. There were no significant differences of glomerular sclerosis, adhesion to the Bowman's capsules in both the MCN and the FSG groups by administration of CsA. Foamy degeneration of endothelial and mesangial cells, epithelial proliferation, hyalinosis and mononuclear infiltration were significantly reduced by CsA in FSG groups. Microcalcification was commonly seen in CsA administrated groups. The main sutype of infiltrated mononuclear cells in glomeruli and interstitium were monocytes in FSG groups. The proportion of T cells were higher in interstitium by disease progression and it was significantly decreased by CsA. On conclusion the most important ultrastructural changes, regarded as the main mechanism of supression of proteinuria is that the CsA stabilize the podocytes, by preventing vacuolar degeneration and focal detatchment. But CsA does not influence the progression of glomerular sclerosis in PAN induced nephrosis.

• Keywords: Minimal change disease;Focal segmental glomerulosclerosis;Cyclosporine A;Puromycin aminonucleoside;Ultrastructure;