Molecular sieve in rat tubular basement membrane as revealed by negative staining

Rat tubuli were isolated both by the method of Krisko and by a modified method of Cook and Pickering; renal tubular basement membrane (TBM) was isolated by sonic disruption and by the method of Carlson. Using electron microscopy after negative staining, TBM of rat kidney isolated under these different conditions was shown to be a fine meshwork. Strands of the meshwork were interwoven, apparently enclosing pores to make up whole basement membrane. These findings are compared with our previous observation that glomerular and alveolar basement membranes were made up of a similarly fine meshwork.