The metabolism of adenosine-8-C14, at relatively high and low concentrations, was studied in human erythrocytes freshly obtained and after 6 and 9 weeks of storage in ACD. At high adenosine concentration (3.6 µM/ml. cells), considerable conversion to ATP was found in fresh and stored cells, suggesting that direct phosphorylation of adenosine occurred, a reaction that is minimal at low (0.36 µM/ml. cells) adenosine concentration because of extensive rapid deamination. Incorporation of the label via hypoxanthine or adenine is unlikely, since at high adenosine concentration no dilution of ATP labeling in the presence of unlabeled inosine (hypoxanthine) was found, nor was free labeled adenine detected in erythrocyte extracts.
A study of the metabolism of adenine-8-C14 in fresh and stored erythrocytes suggests that the presence of a suitable nucleoside (e.g., inosine) is required for efficient utilization of adenine-8-C14 for ATP formation in the erythrocytes of blood stored for prolonged periods.