Objective: Several investigations indicate that glycosaminoglycans (GAG) are important components of the glomerular basement membrane (GBM) and that they play a remarkable role in the control of charge-selectivity in the glomerular capillary wall. In order to evaluate the possible use of GAG as a marker of glomerular disease, we evaluated urinary GAG excretion in 37 patients with systemic lupus erythematosus (SLE) grouped by disease activity and kidney involvement and in 17 healthy controls.
Methods: GAG were isolated from urine by using ion-exchange chromatography on DEAE Sephacel. GAG composition was determined by cellulose acetate electrophoresis and expressed as relative percentages by densitometric scanning of Alcian Blue stained strips.
Results: Total GAG levels were significantly increased only in active extra-renal SLE patients. Qualitative analysis of urinary GAG revealed the presence of a low sulphated chondroitin sulphate-protein complex (LSC-PG), whose frequency was higher in patients compared to controls. Moreover, inactive SLE was characterized by an alteration of the chondroitin sulphate/heparan sulphate ratio.
Conclusion: These variations suggest the presence of an abnormal permeability of the renal filter in patients without other appreciable signs of kidney alteration. Therefore, qualitative-quantitative urinary GAG analysis could represent an additional diagnostic approach.