Variations in chemical composition of human glomerular and tubular basement membranes with age and disease.

Abstract

A graded sieving procedure was used to isolate glomeruli and tubules from renal cortex of men of premature age up to 80 years and of 4 patients suffering from Zellweger syndrome, congenital nephrotic syndrome, polycystic renal disease or diabetes mellitus. Glomerular and tubular basement membranes (GBM and TBM, respectively) were obtained with a detergent procedure. Purity of basement membrane preparations was controlled with light and electron microscopy and by estimating total phosphorus content. Amino acid and carbohydrate composition of the basement membranes were determined and statistically evaluated. Comparison of GBM and TBM from the same kidneys showed at all ages that GBM contains more 3-hydroxyproline, neuraminic acids and mannose. These differences may contribute to the different immunogenic properties of the two basement membranes reported in the literature. Significant changes with age in the chemical composition were found, suggesting that the proportion of collagenous peptide moieties increases and that of noncollagenous peptide moieties decreases with age in both GBM and TBM. In addition, the hydroxylation grade of proline and lysine increases significantly with age reaching an adult level for GBM after 4-6 months of age and for TBM at late childhood. The age-related changes in basement membrane composition may influence functional properties of these extracellular renal structures. The chemical composition of GBM and/or TBM of the 4 patients showed some differences in comparison to control preparations from persons with ages approximating that of the patients.