Chemical characterization of glomerular and tubular basement membranes of men of different ages

Abstract

Pairs of glomerular and tubular basement membrane preparations were obtained from kidneys of individuals of premature age up to 80 years. The purity of the preparations was established with light and electron microscopy and by estimating the total phosphorus content. The amino acid and carbohydrate composition was determined and statistically evaluated for 33 to 38 preparations divided over five age groups. Comparison of glomerular and tubular basement membranes from the same kidneys showed that regardless of age glomerular basement membranes contain more 3-hydroxyproline and more of the heteropolysaccharide constituents neuraminic acids and mannose. These differences cannot be ascribed solely to the presence of a minor amount of interstitial collagen. The chemical composition of the two types of basement membranes changes with age. For the first few years after birth the contents of glycine and total imino acids increase and those of collagen-nonspecific amino acids decrease, whereas constituents of the heteropolysaccharide units do not change markedly. These results suggest that proportions of collagenous and noncollagenous peptide moieties gradually change with age in both glomerular and tubular basement membranes. In addition, the extent of hydroxylation of proline and lysine increases significantly with age, reaching an adult level for glomerular basement membranes after 4 to 7 months of age and for tubular basement membranes during late childhood. The contents of glucose and galactose rise with age to an extent comparable with that of hydroxylysine. The age-related changes in basement membrane composition may influence functional properties of these extracellular renal structures.

Age-Related Changes in Rat Glomerular Basement Membrane Components Solubilised with Pepsin

“…The data obtained in the present investi gation are consistent with the earlier demon stration that the collagenous components of rat G BM increase with age [4], The propor tion of collagenous and non-collagenous peptide moieties changes in G B M prepared from men of increasing age [30]. The content of non-collagenous amino-acids decreases and the degree of hydroxylation increases with age; the rat therefore resembles man in some important respects.…”

“…The content of non-collagenous amino-acids decreases and the degree of hydroxylation increases with age; the rat therefore resembles man in some important respects. Since the agerelated changes in basement membrane composition may influence functional prop erties [30], they should be taken into consid eration in any study of renal function or dis ease. Further studies are required before the interrelationship of the collagenous network of the G BM is understood, but our results emphasise the complexity of this structure and its dynamic nature.…”

Age-Dependent Changes of the Kidneys: Pharmacological Implications

“…On electron microscopic analysis, an increase in focal thickening of both glomerular and tubular basement membranes is observed, probably due to the accumulation of collagen [14]. The total collagen content (as indicated by hydroxyproline concentration) increases with age, too [15].…”

Patients with IgA nephropathy have circulating anti-basement membrane antibodies reacting with structures common to collagen I, II, and IV.

“…Bovine glomerulae were isolated by sieving of ground kidney cortex and were disrupted by sonication as described by Freytag et al (12). Human GBM was isolated from glomerulae by the use of detergents, essentially as described by Langeveld et al (13). In both cases, benzamidine hydrochloride (5 mM), 6-aminohexanoic acid (25 mM), phenylmethanesulfonyl fluoride (1 mM), N-ethylmaleimide (5 mM), and EDTA (10 mM) were included in all steps to minimize proteolytic degradation.…”