RENAL TUBULAR REABSORPTION OF p-AMINOHIPPURIC ACID (PAll) IN THE DOG

¹ Department of Pharmacology, College of Medical Sciences, University of Minnesota, Minneapolis, Minnesota and Department of Pharmacology and Therapeutics, Medical College of Ohio, Toledo, Ohio

A new technique, retrograde intraluminal injection, was developed in order to study reabsorptive transport of organic compounds. Briefly, the technique is performed as follows. Fluid containing a test substance, inulin, and creatinine is injected under pressure (up to 180 mm Hg) into a renal pelvic catheter. The catheter is then occluded for four minutes. On reopening the catheter urine is re-collected serially in 1-ml volumes. The volumes of distribution of the test substances, glucose, and p-aminohippuric acid (PAH), given by retrograde intraluminal injection, greatly exceeded those of inulin and creatinine. Loss of glucose and PAH from injected fluid was most marked in samples derived largely from proximal tubules. PAR given retrogradely was found in venous plasma of the kidney into which it was administered. Probenecid reduced uptake of PAH into plasma and also elevated the concentration pattern of the acid in re-collected urine. Phlorizin elevated the concentration pattern of glucose. The actions of the two inhibitors were specific. We conclude that PAH is reabsorbed by a carrier-mediated process in the proximal tubule. This transport mechanism appears to be located in the peritubular membrane.