Tubular Reabsorption of Protein in Experimentally Produced Proteinuria in Rats

Abstract

Dye-labeling of serum proteins was used to study the role of tubular reabsorption of protein in 2 types of experimentally produced proteinuria. A single intravenous injection of 2.5 mg of T-1824 into normal rats did not cause the blue urine and the kidneys examined 24 hours after the injection exhibited only faint blue staining of the proximal convoluted tubules of the cortex. When mild proteinuria was produced by a single small injection of uranyl acetate, the injection of T-1824 was followed by blue staining of the urine. However, the cortices of the kidneys contained less blue dye than those of control animals, indicating, presumably, that there was less protein reabsorption than normal by the damaged tubular cells. Injection of the blue dye into nephrotic rats with proteinuria due to administration of nephrotoxic anti-rat kidney serum was followed by blue staining of the urine and intense blue staining of the kidneys cortices. This presumably indicated that protein reabsorption by the tubular cells was greater than normal, and that the proteinuria was a result of increased glomerular permeability and not of decreased tubular reabsorption of normally filtered protein.