Glycoproteinuria as an indicator of glomerular basement membrane damage

Urinary glycoprotein was isolated from human urine by the use of the same procedures as those used for isolation of human renal glycoprotein from the glomerular basement membrane (GBM). In Ouchterlony plates and immunoelectrophoretically, human urinary glycoprotein has a common structural component with human renal glycoprotein isolated from GBM. Massive excretion of the glycoprotein in the urine was associated with only two diseases, systemic lupus erythematosus (membranous type) and membranous glomerulonephritis, although it was isolated from the urine of patients with renal as well as nonrenal diseases and normal subjects. In these two membranous diseases, the glycoprotein of GBM could be intensively liberated into the urinary space, as the result of extensive damage of GBM that is initiated by immune-complex deposit. It is discussed that urinary content of this glycoprotein may indicate the degree of the GBM damage in these diseases.