Analysis of Proteinuria in Health and Disease Using Sodium Dodecyl Sulphate—Acrylamide Gel Electrophoresis

Abstract

Abstract. Sodium dodecyl sulphate—acrylamide gel electrophoresis (SDS‐AGE) separates proteins according to their molecular weight (MW) without being influenced by their electrostatic charge. It was carried out on the urine of 17 healthy control subjects and 92 ambulatory patients with suspected or known renal impairment. The SDS‐AGE patterns were classified as physiological, low MW predominance, middle MW predominance, high MW predominance, or mixed low and high MW. Patients were separately classified as having either normal kidneys or glomerular, tubular or mixed renal lesions according to the results of clinical investigation. Comparison of both classifications revealed that SDS‐AGE allowed a correct diagnosis of the site of renal involvement in 83 per cent of cases. Predominantly low MW protein excretion correlated with tubular damage. Middle and high MW patterns correlated with glomerular disease, and a relationship between nephrotic syndrome with minimal glomerular changes and middle MW pattern was found in two cases, suggesting that SDS‐AGE could be used to evaluate the selectivity of proteinuria. However, the estimation of selectivity by SDS‐AGE should be studied in a sufficient number of cases and compared with measurements of selectivity by the protein clearance method.