[Physiological proteinuria. Data of acrylamide-SDS gel electrophoresis and other methods of qualitative and...

Since detection of the first stage of nephropathies requires an exact definition of physiological proteinuria, this has been sought in 97 healthy individuals. Measured by a modification of the biuret reaction, physiological proteinuria did not exceed 100 mug/min in the recumbent position (average of 24.5 mug/min) and 150 mg/24 h (average of 51 mg/24 h). No significant differences were seen with respect to age or sex. Qualitative analysis of urinary proteins was done by cellulose acetate electrophoresis, immunoelectrophoresis and polyacrylamide-SDS electrophoresis. This latter method has the great advantage of classifying the proteins according to their molecular weight, wtihout electrostatic interference. Its graphic representation delineates a normal zone allowing an objective distinction between physiological and pathological proteinurias. In the majority of cases, the proportion of albumin is between 25 and 55%. The orthostatic position increases proteinuria (average of 41 mug/min) with a tendency to a distribution which erroneously suggests a glomerulopathy. Accordingly, investigation for small changes in proteinuria should always be carried out on urine formed in the recumbent position.