RENAL TUBULAR EXCRETION STUDIES WITH PYRIMIDINE DERIVATIVES AND ANALOGS

¹ Department of Pharmacology, University of Pennsylvania, Schools of Medicine, Philadelphia, Pennsylvania
² Department of Pharmacology, University of Kansas Medical Center, Kansas City, Kansas
³ Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut

Renal tubular excretion of the ribonucleoside of 6-azauracil (azauridine), orotic acid and a degradation product of 6-azauradil, glyoxylic acid semicarbazone, was demonstrated in chickens during infusion of these compounds into the renal portal circulation of one kidney. The tubular excretion of each of these compounds was inhibited by the simultaneous infusion of probenecid. The tubular excretion of azauridine was also inhibited by large infusion loads of p-aminohippurate. When a dilute solution of azauridine was infused together with a large amount of orotic acid, the excretory pattern of azauridine was altered in a way which suggested, among other possibilities, the active tubular reabsorption of azauridine, as well as its active excretion by the tubules, and the inhibition of the reabsorptive process by orotic acid. A similar situation obtained with respect to the excretion of orotic acid, when this was challenged with large infusion loads of azauridine.