Effect of pH on Preservation of Red Cell ATP*

Human blood has been stored in citrate‐dextrose anticoagulants resembling NIH formula‐B, but with varying hydrogen ion concentrations. At a storage temperature of 4 C, a preservative pH of 5.0 was found to be optimal for ATP preservation. At a temperature of 37 C in contrast, a preservative pH of 7.0 or 7.9 was most favorable for maintenance of ATP levels. If adenine was added to the preservative mixture, the optimum was found to be 5.5 rather than 5.0. It was found that a change in temperature resulted in a striking pH shift, so that optimal storage pH both at 37 C and at 4 C was approximately 7.5, provided the pH measurements were made at the storage temperature. The pH optimum of the ATPase system was not found to vary with temperature, and the rate of glycolysis was increased at higher pH levels at 4 C as well as at 37 C. These studies emphasize that as any component of the blood preservative mixture is changed, as when adenine is added, limiting factors in preservation may be altered, and the other conditions of storage must be re‐investigated.