Adenine in Red Cell Preservation

Purine nucleosides have been reported to extend the preservation of red cells stored in acid citrate dextrose (ACD) (1-6). This effect was originally attributed to the production of phosphorylated ribose as an energy substrate within the erythrocyte (7-9) through the action of nucleoside phosphorylase (10). This enzyme was shown to act on inosine, guanosine (11, 12), and on adenosine after its conversion to inosine by the adenosine deaminase of the erythrocyte (3, 13-19). Since inosine was the preferred substrate over guanosine ( 11 ) and was much less toxic than adenosine (2, 3, 16, 18, 20), it was selected as the most suitable of the nucleosides for red cell preservation. Indeed, the initial studies indicated that inosine produced satisfactory preservation for 42 days and was even more effective than adenosine in regenerating depleted organic phosphate esters in erythrocytes stored for 25 days (3, 11). While it is well established that purine nucleosides provide phosphorylated pentose as a source of energy for the red cell, subsequent observations suggested that the viability effects could not be explained by this mechanism. In the first place, the original viability results with inosine (3) could not be reproduced. Thus, in a subsequent investigation (5), only 4 of 23 units stored with inosine were satisfactorily preserved after 6 weeks, thereby raising the question of variability in the composition of the inosine prepara-