The metabolism of 4-aminopyrazolo(3,4-d)pyrimidine in normal and neoplastic tissues.

several normal and neoplastic mouse tissues. APP is rapidly cleared from the peritoneal fluid and blood after intraperitoneal or intravenous administration. The drug is taken up by the blood cells and is lost from them less rapidly than from serum. Approximately one-half of the administered drug is excreted in the urine from nor mal mice in 24 hours, and one-half of this is within the 1st hour. The rate and amount of excretion from tumor-bearing mice are much less. The distribution of APP in the tissues was studied. Only in the tumor cells, small intestine, liver, and spleen did APP concentration increase during the first hour after administration. The following were tentatively identified as metabolites of APP in the tissues: free APP, APP-riboside, 4-hydroxypyrazolo(3,4-¿)pyrimidine, the mono-, di-, and tri': phosphates of APP-riboside, and two unidentified degradation products.