Proteinuria in pigs with experimentally induced renal damage.

Proteinuria was studied experimentally in pigs with renal damage induced by maleic acid, potassium dichromate and by 5/6 nephrectomy. The methods used were: analysis of total protein, immunochemical quantitation of a porcine low molecular weight (alpha-PLMW) protein, agarose gel electrophoresis, and gel chromatography of concentrated urine samples. The urinary clearance of the alpha-PLMW protein in normal pigs was considerably higher than LMW protein clearance in normal man. No increase was seen after surgery. The induction of proximal tubular damage resulted in an increased excretion of, above all, high molecular weight proteins (greater than or equal to albumin) but also of low molecular weight proteins. The highest increase in alpha-PLMW clearance was seen immediately after 5/6 nephrectomy, and the increased alpha-PLMW excretion in pigs with proximal tubular dysfunction was better correlated to creatinine clearance than to the degree of phosphaturia or glucosuria. The results suggest different renal handling of plasma proteins in pigs and humans.