Urinary glycosaminoglycans in patients with systemic lupus erythematosus.

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.