Protein metabolism in the mammalian kidney.

The concentrations of amino acid and polypeptide nitrogen in plasma samples from the aorta, renal vein, and inferior vena cava of the rabbit have been determined. It was demonstrated that there were significantly higher concentrations of amino acids and polypeptides in the renal vein than in either aorta or inferior vena cava. The possible implications of these findings in relation to the role of the kidney in protein metabolism has been discussed.

Filtration and reabsorption of protein by the kidney.

Plasma proteins of the rat have been labelled by the in vivo injection of the dye T-1824. From a study of the rate of disappearance of T-1824 from the circulating blood, and the total T-1824 content of the perfused kidney the rate of protein reabsorption from the glomerular fluid by the cells of the renal tubule has been calculated. It is concluded that protein reabsorption by the cells lining the proximal convoluted tubule of the rat kidney proceeds at a rate of at least 5 mg.

Studies on the mechanism of experimental proteinuria.

When renin is administered intramuscularly to the rat, massive proteinuria occurs without a significant elevation of mean arterial blood pressure. The intravenous administration of renin to normal rats results in a great increase in urinary protein excretion. This response to renin is abolished by bilateral adrenalectomy.

An electrophoretic study of urinary protein in the rat.

The nature of the proteins present in the urine of the normal rat has been investigated by electrophoretic analysis and by fractional precipitation of these proteins by ammonium sulfate. Components similar to serum alpha- and beta-globulin constitute the major portion of the urinary protein in both male and female rats. Following the intraperitoneal injection of renin, a massive proteinuria occurs.