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

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.