Influence of the tubular flow rates on the endocytic uptake and the excretion of horseradish peroxidase by rat kidney

Abstract

Summary The renal clearances of horseradish peroxidase (HRP) in diuretic and anti-diuretic rats were compared with the concentrations of HRP in the renal cortex of the same rats. The injection of mannitol, hypertonic saline, or antagonists to histamine and serotonin, together with HRP, caused diuresis. The renal clearance of HRP was 7–15% of the inulin clearance, relatively small amounts of HRP were reabsorbed into the renal cortex, and relatively large amounts were excreted in the urine. However, when HRP was injected alone causing vascular leakage and anti-diuresis, 6–10 times higher concentrations of HRP were found in the renal cortex, and only a few percent of the protein were excreted in the urine during the first 20 minutes after injection. It is suggested that the low or high endocytic uptake of HRP by the renal cortex was related to the high or low tubular flow rates during diuresis or anti-diuresis.