Persistence of Amethopterin in Normal Mouse Tissues.

Summary1. Amethopterin given parenterally in various doses to normal mice resulted in the retention of a more or less constant amount of amethopterin in the liver for a period of at least 3 weeks. A decrease in the kidney concentration of amethopterin was noted. 2. CF at doses ranging from 0.5 to 30 mg/kg intraperitoneally failed to have any detectable effect 24 hours later on the concentration of amethopterin in the liver and kidneys, but caused a significant rise in the serum level of amethopterin. 3. The inhibitory substance present in the mouse liver 24 hours to 14 days after the administration of amethopterin has the same Rf value as amethopterin in 3 different solvent systems, and is therefore considered to be amethopterin.