Colorimetric investigation of the uptake of an intravenously injected protein (horseradish peroxidase) by rat kidney and effects of competition by egg white.

After intravenous injection of horseradish peroxidase into rats, the foreign protein appeared in the kidney first in the small phagosomes and its concentration there decreased quickly; it then was concentrated and "stored" for several days in the large phagosomes. After injection of 10 mg of peroxidase per 100 gm of body weight, the concentration of peroxidase in blood and urine decreased exponentially during the first 6 hours; small amounts of peroxidase were excreted in the urine for several days. When 0.05 to 1.0 mg of peroxidase per 100 gm were administered, most of the peroxidase was taken up by the liver and little by the kidney, and a portion was excreted in the urine even at the lowest dose. At doses above 1.5 mg per 100 gm, the liver cells were saturated, and large reabsorption droplets appeared in the tubule cells of the kidney. With further dosage increase, the concentration of peroxidase in the phagosomes of the kidney increased rapidly until saturation was reached at doses of 13 mg per 100 gm. After intraperitoneal injection of egg white 18 hours prior to the administration of peroxidase, the concentration of peroxidase in all kidney fractions was only 10 to 25 per cent of the values for the untreated animals, the disappearance of peroxidase from the blood was delayed, and 81 percent more peroxidase was excreted in the urine. The treatment with egg white had no effect on the uptake of peroxidase by the liver. The ability of kidney tissue to degrade and adsorb peroxidase in vitro was tested.