The effects of protein extraction on the structure and filtration properties of renal basement membranes.

Basement membranes were isolated from rabbit kidney using the detergent N-dodecyl sarcosine. Treatment of the membranes with 6 M urea or 5% sodium dodecyl sulphate in the presence of reducing agent at 37 degrees C extracted approximately 50% of the protein. Amino acid analysis and polyacrylamide gel electrophoresis demonstrated that the residual proteins were collagenous and of molecular weight. Extracted membranes retained their continuity of structure and exhibited a matrix composed of fibrous and globular elements when examined by electron microscopy. When the filtration properties of the membranes were studied in vitro they showed an enhanced capacity to retain proteins. The results suggest that basement membranes contain a matrix of fibrous proteins, which is responsible for the sieving characteristics of the native membranes.