4-Amino-5-imidazolecarboxamide (l), an amine found to accumulate in bacterial systems poisoned either by sulfonamides (2, 3) or aminopterin (4), has been suggested as an intermediate of purine synthetic reactions (5, 6). Although the metabolic inertness of the carboxamide’ in certain bacterial systems (7, 8) led to the belief by some (8) that this compound was an aberrant product of metabolism ...

Urinary purine excretion has been determined for four normal subjects, for thirteen patients with different types of acute and chronic leukemia, and for one man with mycosis fungoides by means of paper chromatography. Differentiation between types of leukemia, based on punine excretion, was not conclusive. Increases in 1-methylhypoxanthine and 8-hydroxy-7-methylguanine in nearly all patients, a...

Rates of purine synthesis de novo, as measured by the incorporation of [14C]formate into newly synthesized purines, have been determined in cultured human fibroblasts derived from normal individuals and from patients deficient in adenosine deaminase, purine nucleoside phosphorylase, or hypoxanthine phosphoribosyltransferase, three consecutive enzymes of the purine salvage pathway. All four type...

1. This review focuses on the extracellular actions of ATP and adenosine, and in particular their role in cardiovascular regulation. 2. ATP serves as a co-transmitter within the sympathetic nervous system, and is also released from endothelium and aggregating thrombocytes. ATP acts on P2x purinoceptors on vascular smooth muscle cells to induce vasoconstriction. Stimulation of P2y purinoceptors ...