Tubule-derived membrane glycoproteins in the urine of patients (including those with AIDS) as analysed by radioimmunoblotting

As a contribution to the noninvasive diagnosis of kidney damage, polyclonal antisera specifically directed against brush border surface glycoproteins of the proximal tubule of the human kidney were used in radioimmunoblotting studies for the assessment of kidney-tissue proteinuria. Urine specimens from healthy controls, from patients (n = 41) with various forms of renal involvement and from those suffering from symptomatic HIV-infection (AIDS) but having normal kidney function, were investigated for the excretion of kidney-derived membrane proteins. After SDS-polyacrylamide gel electrophoresis of urine samples and electroblotting of protein bands on nitrocellulose sheets, followed by incubation with the antibody and subsequently with 125I-labelled protein A, 3 major tubular glycoproteins (Mr 240 000, 160 000, 120 000) were revealed by autoradiography. The results indicate and increased shedding of epithelial membrane glycoproteins in the urine of patients with kidney lesions, and they also demonstrate the suitability of radioimmunoblotting for the determination of such tissue-antigens ("brush border-histuria").