Synthesis and metabolism of quinolinic acid ring labeled with tritium.

Abstract

Summary1. Quinolinic acid was labeled in the 4, 5, and 6 positions with tritium by the neutron recoil method. 2. Intraperitoneal injection of labeled quinolinic acid into rats was followed by excretion of labeled N1 methylnicotinamide in urine during the next 24 hours. Tritium contents of excreted N1 methylnicotinamide in 2 experiments indicated that 7.6 and 23.6% originated from the injected labeled quinolinic acid. The evidence is definite that quinolinic acid can serve in the rat as a source of niacin. 3. Most of the injected quinolinic acid was exreted as such in the urine. Quinolinic acid isolated from urines of 2 rats had specific activities of 103 and 112% of injected quinolinic acid. The increase in specific activity suggests that tritium-labeled quinolinic acid may have been less rapidly metabolized than the unlabeled substance.