Regional Variation in Human Extracellular Purine Levels

The selective toxicity of purine deoxynucleoside to specific lymphocyte cell populations and recent evidence that purine nucleosides are important extracellular modulators of neurotransmission and coronary blood flow have prompted measurement of extracellular purines in man. By using a highly sensitive fluorimetric assay and collecting specimens into an inhibitor of adenosine deaminase, we have accurately measured purine nucleoside and hypoxanthine-xanthine levels in arterial and venous blood, in cerebrospinal fluid and in bone marrow aspirates. In peripheral venous plasma from normal volunteers, purine levels average 2.7 +/- 1.2 microM (mean +/- S.D.) with 38% in the form of adenosine and 47% as hypoxanthine and xanthine. Arterial purine levels are similar to those in mixed venous plasma; however, the hypoxanthine-xanthine component is reduced compared to simultaneously drawn mixed venous specimens (p less than 0.005). Hepatic venous plasma tends to have higher purine levels than does peripheral venous plasma (not significant), whereas bone marrow aspirates have 10-fold higher hypoxanthine-xanthine levels, suggesting that bone marrow may be a major source of plasma purines. Cerebrospinal fluid hypoxanthine-xanthine is twofold to eightfold higher than mixed venous levels, whereas adenosine levels are lower (p less than 0.01 and p less than 0.025, respectively).