Glycosaminoglycans in urine and amniotic fluid in congenital nephrotic syndrome of the Finnish type.

The heparan sulphate proteoglycan (HSPG) of the glomerular basement membrane (GBM) is considered to be mainly responsible for the charge selectivity of the GBM; decreased HSPG results in a decreased anionic charge of the GBM with increased heparan sulphate (HS) in the urine and is believed to be responsible for the proteinuria of the congenital nephrotic syndromes (CNS). Urinary HS and chondroitin sulphate (CS) concentrations in children with CNS of the Finnish type (CNF) and the total glycosaminoglycans (GAG) in amniotic fluid of CNF pregnancies were measured by three methods: Alcian blue, Safranine O and uronic acid assays. The total urinary GAG in CNF and other nephrotic patients was comparable to controls with all three methods. Urinary CS and HS in CNF did not differ significantly from controls. Total amniotic fluid GAG was also similar in CNF and control pregnancies. These results suggest some pathogenetic mechanism other than loss of glomerular HS chains in urine for the proteinuria of CNF.