Ultrastructural study of glomerular basement membrane in diabetic rats by the quick-freezing and deep-etching method

The three-dimensional ultrastructure of glomerular basement membrane (GBM) and mesangium in very early stage of streptozotocin-induced diabetic rat kidney was examined by the quick-freezing and deep-etching method. In control rats GBM was composed of three layers. Outer and inner layers consisted of files of fibrils that connected endothelial or epithelial cells perpendicularly with meshwork of a middle layer that also consisted of dense meshwork structure composed of fibrils. In diabetic rats, perpendicular fibrils of the inner layer were irregular and disrupted, and the layer was enlarged. The meshwork structure of the middle layer was irregularly enlarged, and matrix fibrils were disrupted. Early insulin treatment prevents these morphological changes. Furthermore, early administration of beraprost sodium, a PGI2 analogue, might have beneficial effects in preventing the progression of these changes.