The relationship between glomerular function and podocyte structure of pre-proteinuria and acute nephrosis in puromycin aminonucleoside-induced rat models: a comparative electron microscopic study.

Puromycin aminonucleoside (PA) has been generally utilized as model of podocyte injury followed by massive proteinuria, severe damage on endocytotic activity of epithelial cells and postmodification of endocytosed compounds. However, total PA nephrosis (PAN) mechanism cannot be understood. We aimed to study glomerular function, foot process degeneration and transport pathways of podocytes in pre-proteinuria and acute PAN rats. Eighteen male Wistar albino rats were divided into three groups: control, pre-proteinuria and acute nephrosis groups (n=6). PA was injected into pre-proteinuria group for three times and acute group for nine times. Proteinuria levels in urine, creatinine and albumin levels in blood were detected 24 hours after PA injections. Renal cortex samples were prepared for transmission electron microscopy. Proteinuria levels in acute group significantly elevated, whereas creatinine clearance, serum albumin levels and urine volumes diminished compared to control and pre-proteinuria groups. In pre-proteinuria group, hypertrophy and structurally rich cytoplasm were detected only within podocytes. Acute group had various protein absorption granules secreted from podocyte cytoplasm to the urinary space through exocytosis after lysosomal digestion; but not observed in pre-proteinuria group. The number of slit pores in pre-proteinuria group decreased, particularly related to fusion of foot processes, subsequently leading to proteinuria. We concluded that foot process fusion begins prior to development of proteinuria although their serum albumin and creatinine clearance levels do not differ significantly. Additionally, we suggested that in acute PAN, first affected glomerular cells could be podocytes and there could be a correlation between glomerular function and number of slit pores.

Experimentally induced puromycine aminonucleoside nephrosis (PAN) in rats: evaluation of angiogenic protein platelet-derived endothelial cell growth factor (PD-ECGF) expression in glomeruli.

BACKGROUND: In experimentally induced puromycine aminonucleoside nephrosis (PAN) animal models, nephrotic syndrome with minimal change disease and focal and segmental sclerosis-like nephritis similar to that in human is demonstrated; however, the real mechanism of PAN is not yet elucidated. Platelet derived endothelial cell growth factor (PD-ECGF), an endothelial mitogen protein, is believed to take part in microvessel formation and in stimulation of angiogenesis and its expression has not been totally demonstrated in PAN rats yet. In this study, we aimed to examine PD-ECGF expression in acute and chronic PAN induced in rats and find out the association between its expression and the stages of angiogenesis in kidney. METHODS: For the experiment, twenty-four Male Wistar Albino rats were used and divided into four groups; control group (n = 6), pre-proteinuria group (n = 6), acute group (n = 6) and chronic group (n = 6). We compared statistically all data by One-way ANOVA Test followed by Dunn Multiple Comparison Test. RESULTS: Proteinurea levels in control and pre-proteinuria groups were not statistically different; however, it was remarkably higher in the acute nephrosis group and significantly greater in the chronic nephrosis group than control group (p < 0.0025). In pre-proteinuria group, the serum albumin and creatinine clearances also did not significantly differ from the control group. On the other hand, in the acute and chronic nephrosis groups, serum albumin and creatinine clearances progressively decreased (p < 0.05). In our immunohistochemical studies, we showed elevated PD-ECGF expression in glomeruli of acute and chronic PAN rats. Microscopic and ultrastructural appearances of the glomeruli of acute and chronic PAN showed various sequential steps of angiogenesis, macrophages and immature capillaries with primitive lumens and apoptotic endothelial cells in the increased mesangial matrix. CONCLUSIONS: It is reported that acute and chronic PAN progressively increase PD-ECGF expression and following induction of angiogenesis in the affected glomeruli.