Ultrafiltrable adenosine triphosphate and 2,3-diphosphoglycerate concentrations in cold-stored human erythrocytes

Free ATP and DPG concentrations in ACD-preserved human erythrocytes (rbc) were estimated by measuring these organic phosphates in ultrafiltrates of cell lysates prepared at 0 to 2 C. The free ATP concentration in hypotonic hemolysates decreased from 0.59 to 0.08 mumol/ml rbc during four weeks of cold storage. In French Pressure Cell lysates, free ATP increased from 0.23 to 0.47 mumol/ml rbc in the first week and then declined to 0.12 mumol/rbc during the following three weeks. In two weeks, the free DPG level decreased from 0.64 to 0.41 mumol/ml rbc in hypotonic lysates and from 1.08 to 0.15 mumol/ml rbc in French Pressure Cell lysates. It is proposed that, as total DPG concentration decreases during cold storage, free ATP concentration also decreases due to increased ATP binding to hemoglobin sites vacated by DPG. It is suggested that it is the change in the free rather than the total ATP which may be more relevant to the metabolism of the cold-stored erythrocyte.