Fibrillar ultrastructure of the glomerular basement membrane of the rat kidney as revealed by digestive treatment.

Rat kidney glomerular basement membrane (GBM) was isolated and digested with alpha-amylase and elastase. Electron microscopy revealed a meshwork structure composed of fibrils 3 nm in width. They appeared to be type IV collagen fibrils. We succeeded in clarifying a significant ultrastructural aspect of the GBM which had been unclear until now. The findings are consistent with our previously proposed GBM molecular sieve theory.