Immunological and ultrastructural analysis of loss of tubular membrane-bound enzymes in patients with renal damage.
The pathophysiological background of shedding of membrane-bound enzymes from the proximal tubule was assessed in urine specimens of patients with renal damage applying immunospecific affinity-chromatography, immunotitration, ultracentrifugation, electroimmunodiffusion, immunohistology, as well as negative staining technique. Compared to healthy controls, patients with kidney injury, e.g. after administration of potentially nephrotoxic drugs (cytostatics, contrast media) revealed an increased excretion rate of vacuolar membrane fragments (50-500 nm) into urine. The brush border (BB) of the proximal tubule was identified as a main source of urinary blebs as concluded from immunoelectrophoretic and immunohistochemical analysis. In addition, the marker enzyme profile of urinary vacuolar blebs was similar to that of the BB membrane from human kidney. The results further evidenced that, during the initial phase of tubular injury, 5-10 nm surface glycoproteins of the BB, among them Ala-Leu-aminopeptidase and portions of gamma-glu-transpeptidase, are released into urine; this might be followed by increased blebbing of macromolecular BB fragments, indicating more severe membrane disruption.
Scherberich
J E
JE
Klinikum der Johann W. Goethe-Universität, Abteilung Nephrologie, Frankfurt am Main, FRG.
D005260:Female; D006801:Humans; D007425:Intracellular Membranes / Q000473:pathology; D007674:Kidney Diseases / Q000201:enzymology* / Q000473:pathology / Q000652:urine; D007687:Kidney Tubules, Proximal / Q000201:enzymology* / Q000473:pathology / Q000648:ultrastructure; D008297:Male; D008871:Microvilli / Q000201:enzymology; D011507:Proteinuria / Q000209:etiology