Metabolism by the Rabbit of Intravenously Administered Adenine

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Abstract
A study was made of the metabolism by the rabbit of adenine administered intravenously at a dose of 35 mg/kg with 100 .mu.Ci of 8-14C-adenine. The infused adenine was removed from the blood in 2 phases, 1st by diffusion into the tissues and 2nd by metabolic reactions throughout the body. The adenine equilibrated within a few seconds equally between plasma and red blood cells and between them and kidney, liver, duodenum, lung and heart. Diffusion into skeletal muscle was much slower and into brain slowest. The more gradual disappearance of adenine from blood, and from the rest of the body, with a half-life of about 20 min and with complete removal by 2 h, was along 3 pathways, leading to, after 4 h: 74% in adenine nucleotide (mostly AMP, ADP, and ATP); 12% as unchanged adenine in the urine; and 11% as a mixture in almost equal parts of 8-oxyadenine and 2,8-dioxyadenine in the urine. Conversion of adenine to adenine nucleotide, probably by initial reaction with phosphoribosyl pyrophosphate and adenine-phosphoribosyl-transferase, was at widely different rates in the organs with duodenum, kidney, liver, and lung high and heart, red blood cell, skeletal muscle and brain relatively low. Sites of formation of the two oxyadenines, probably by action of xanthine oxidase, were not determined.