Control of Artifacts in Plasma Adenosine Determinations

Abstract The literature concerning the role of adenosine (ADO) in physiology reveals no agreement about plasma ADO concentrations and suggests two main sources of error in these determinations: rapid ADO uptake by red blood cells or rapid ADO production from ADO nucleotides, which may be released by any cell lysis or platelet aggregation during plasma preparation. We therefore studied ADO concentrations in plasma from normal human forearm venous blood. ADO was determined by a highperformance liquid chromatographic procedure with a sensitivity of 3 nM (original plasma). Observed ADO concentrations ranged from 894 nM to 8.2 nM depending on the conditions of plasma preparation. In plasma prepared in plastic tubes from 4.5 ml of blood drawn into a plastic syringe containing 1.5 ml of an isotonic stopping solution (pH 7.4) containing heparin (60 units ml), dilazep (40 μM), EGTA (40 μM, EDTA (40 μM), erythro-9-(2-hydroxy-3-nonyl) adenine (40 μM), and α,β-methylene adenosine-5′-diphosphate (525 μM), the plasma ADO concentration was 13.3 ± 1.88 nM (SE) after correction for a simultaneous ADO recovery determination. The mean ADO recovery was 78% ± 3.39. The mean plasma ADO concentration found by this method of collection and preparation is lower then reported by others. Proper collection methods are required to avoid artifacts when determining plasma ADO concentrations.