To elucidate morphologic changes in glomeruli of rats made diabetic with alloxan 40 mg/kg, we examined the filtration barrier with light microscopy, transmission (TEM), and scanning electron microscopy (SEM). The rats were killed at 10 or 20 weeks. The presence of diabetes was verified by blood and glucose measurements. In vivo pefusion was carried out through the left ventricle with gluteraldehyde in cacodylate buffer. SEM and TEM were performed by conventional techniques. SEM revealed striking changes in both the epithelial and endothelial surfaces which were focal and progressive with time. The epithelial surfaces showed podocyte fusion with areas of frank necrosis. Occasional areas of regeneration were seen. The endothelium showed a loss in number and decrease in size of fenestrate, proliferation of microvilli, and appearance of irregular cellular processes. TEM confirmed the presence of cellular changes. The basement membrane was irregularly thickened and the mesangium ws more prominent than in control animals. We conclude that not only is the basement membrane affected by diabetes, but also important endothelial and epithelial cell changes occur as well. These changes are best appreciated by SEM and have not been previously described.
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