The distribution and utilization of adenine in red blood cells during 42 days of 4 C storage

The fate of adenine in CPD whole blood (17.3 mg/500 ml, or 0.25 mM) was evaluated during 42 days of 4 C storage. In whole blood, 95 per cent of the adenine was removed from the plasma by 42 days while the cellular adenosine triphosphate (ATP) levels remained above 60 per cent of the initial concentration. Packed red blood cells (concentrates) were stored with the same relative quantity of adenine (0.1 mg/ml red blood cells) used in whole blood units by the addition of adenine after packing and were shown to take up adenine in a similar manner. Calculations of the initial adenine distribution indicated higher intracellular adenine concentrations than predicted from distribution equilibrium based on volume considerations. The presence of inorganic phosphate has marginal effects on adenine incorporation but does elevate ATP levels, while contributing to the reduction of 2,3-diphosphoglycerate (2,3-DPG) content. The free adenine equilibrium between plasma and red blood cells favors the red blood cells, suggesting adenine binding by red blood cell membranes as shown by initial distribution studies with 14C-adenine and equilibrium dialysis.