Salvage of circulating hypoxanthine by tissues of the mouse

Hypoxanthine is an inefficient precursor of purine nucleotides in mouse tissues. In vitro, mouse erythrocytes salvage less than 10% of hypoxanthine (10 microM) added to whole blood in 30 min of incubation at 37 degrees C. In vivo, circulating hypoxanthine is rapidly degraded (greater than 90% in 10 min) to allantoin and uric acid. All tissues examined (other than erythrocytes) converted small amounts of hypoxanthine to nucleotides, with kidney and lung being the most active tissues examined. It is estimated that less than 2% of circulating hypoxanthine is salvaged in the mouse; the remainder is catabolized.