Glomerular basement membrane: biosynthesis and chemical composition in the streptozotocin diabetic rat.

Abstract

A B S T R A C T To study the effect of streptozotocin induced diabetes on glomerular basement membrane (GBM) synthesis, an isolated rat glomerular preparation has been developed, and its metabolic properties have been defined. The chemical composition of normal rat GBM isolated from this preparation closely resembles human GBM. Incubation with [U-'4C1 lysine leads to prompt incorporation of label into GBM and the subsequent appearance of labeled hydroxylysine. A 1-h lag before detection of labeled hydroxylysine in GBM suggests a delay in the release of GBM precursors. Significantly lower counts appeared in the nondialyzable fraction of the medium than in insoluble GBM during pulse-chase experiments, and labeled hydroxylysine accounted for a lower portion of the total counts in the medium (0.85%) than in the GBM (1.98%).Isolated glomeruli were prepared from streptozotocin diabetic rats of 4-6 wks duration. After incubation with [U-'4C] The chemical composition and morphology of the GBM was then studied in rats with long term streptozotocin diabetes (14 mo) to determine if the increase in hydroxylysine and glucosyl galactose and the decrease in lysine previously noted in the GBM in long-term human diabetes occurs in the rat. Except for minor changes in proline and arginine content, the chemical composition of diabetic rat GBM did not differ from age matched controls. while light microscopic studies of diabetic and control kidneys revealed equal degrees of mesangial and peripheral GBM changes. INTRODUCTIONPathologic changes in the capillary wall characterized by thickening of the basement membrane have been recognize(l in multiple vascular beds of long-term diabetics (1, 2). Diabetic intercapillary glomerulosclerosis and restultant renal failure, however, continue to be the greatest single cause of mortality and morbidity in patients with the juvenile onset type of diabetes (3,4 In addition to the basement membrane thickening observed in patients with diabetes mellitus, a distinct chemical change has been described in the GBM of some patients with diabetes of long duration (14,15). The diabetic GBM shows an increase in hydroxylysine with a concomitant decrease in lysine residues as well as an increase in the disaccharide glucosyl-galactose covalently bound to hydroxylysine. In addition, significant increases in GBM hydroxyproline and glycine content and decreases in valine and tyrosine are also observed in diabetic GBM. Since a subunit rich in glucosyl-galactose, hydroxylysine, glycine, and hydroxyproline and poor in lysine, valine, and tyrosine has been described in bovine GBM (16), it is possible that the change in diabetic GBM could represent accumulation of a similar carbohydrate rich subunit. No information on the chemical composition of GBM in experimental animals with longterm diabetes is currently available.Our current information regarding the control of GBM biosynthesis is inadequate. Several studies which utilized experimental animals have suggested that the thickening of basement membrane in diabetes ...

Glomerular Basement Membrane Turnover in Young, Old, and Streptozotocin-Diabetic Rats

“…Hence it is interest ing to note that in vivo incorporation exper iments revealed a diminished formation of liver and serum proteins as well as of colla gen type I under diabetic conditions [11,13,16,21,22,24,26,28], In contrast to these observations, most of the findings obtained by in vitro studies detected a raised GBM synthesis in diabetic metabolism [1,3,5,10,12], Isolated glomeruli of diabetic rats incor porate more specific GBM tracer than glo meruli of the controls.…”

“…The biochemical analyses of the GBM revealed a higher content of hydroxylated amino acids, especially OH-lys, in the old and diabetic animals. The findings suggest that diabetic and senile glomerulosclerosis results from a prolonged turn over of the GBM and GBM-like material under the altered metabolic conditions investi gated in this study.While work in several laboratories has established the ability of isolated glomeruli to synthesize glomerular basement mem brane (GBM) in vitro [1,3,5,10,12], very little is known about the production and breakdown of this structure in vivo, espe cially with regard to the changes which may occur in diabetes mellitus. In this respect, the in vitro and in vivo findings are even contradictory.…”

Long-term effects of untreated diabetes on the arterial wall in rat

“…However, more advanced glomerular epithelial lesions have been found in rats with long-term alloxan diabetes than in age-matched control animals [27]. On the other hand, normal rates of glomerular basement membrane synthesis have been described in the rats with streptozotocin diabetes [28]. Further studies are needed to clarify whether the thickening of basement membrane has some role in the acceleration of atherosclerosis in the diabetic state.…”

Composition and Biosynthesis of Glomerular Basement Membrane in Rats Fed Diets Rich in Sucrose

“…The present studies were initiated to de termine the long-term effect of SU feeding on the composition and post-translational modification of GBM in SU rats since these parameters are known to change in diabetic animals [20][21][22], The subunit composition ofGBM is modified by the administration of lathyrogens [23] and during aging [24] and we, therefore, undertook a comparison of the subunit pattern on polyacrylamide gel electrophoresis of GBM prepared from SU and ST fed rats. Since the development of microangiopathy is a slow process in man we undertook a long-term study involving the maintenance of rats on control (ST) and experimental (SU) diets for 8 months.…”