Chemical compositions of glomerular and tubular basement membranes of human kidney.
Glomerular basement membranes (GBM) and tubular basement membranes (TBM) were prepared from human kidney and their chemical compositions were studied. Electron microscopic figures showed no contamination of the cellular components components or collagen fibers, indicating a high degree of purity of the preparations. Low contents of phospholipid supported this indication. Amino acid compositions of the human GBM and TBM resembled that of the bovine GBM, containing hydroxyproline, hydroxylsine, half-cystine, methionine and a large amount of glycine as the characteristic amino acids. The human GBM and TBM had similar carbohydrate compositions consisting of glucose and galactose, as the major sugars, together with mannose, L-fucose, hexosamine and sialic acid. Glucosylgalactosylhydroxylysine and a small amount of galactosylhydroxylysine were detected in alkaline hydrolyzates of both membranes. The human GBM and TBM separated into more than ten subunits having molecular weights ranging from 2.5 times 10-4 to more than 2.5 times 10-5 on polyacrylamide gel electrophoresis in the presence of sodium laurylsulfate and 2-mercaptoethanol. The electrophoretograms of both membranes resembled that of the bovine GBM. These observations indicate that the human TBM has a similar chemical structure to those of the human GBM and the bovine GBM.