Lysosomal enzymes in human urine: evidence for polymorphonuclear leucocyte proteinase involvement in the pathogenesis of human glomerulonephritis.

1. Lysosomal proteinase activity was assayed in human cadaver kidney, urine, granules from poly­ morphonuclear leucocytes of normal persons, and urine samples from 154 patients with renal disease. 2. Granules from polymorphonuclear leuco­ cytes showed proteinase activity at acid and neutral pH, whereas cadaver kidney showed proteinase activity at acid pH only. 3. The urine from 13 patients with glomerulo­ nephritis showed proteinase activity at both acid and neutral pH as well as increased amounts of antigenic glomerular basement membrane frag­ ments. The properties of the urinary proteinases suggested that they had originated in polymorpho­ nuclear leucocytes. 4. Only the urine samples containing these proteinases were capable of degrading isolated human glomerular basement membrane in vitro. 5. Clinical recovery, where it occurred, was ac­ companied by the disappearance of urinary proteinase activity, and reduction in glomerular basement membrane antigen excretion.