Lack of success with a combination of alanine and phosphoenolpyruvate as an additive for liquid storage of red cells at 4 degrees C

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Abstract
Red cells were stored at 4.degree.C in a storage solution containing alanine or alanine plus phosphoenolpyruvate (PEP). The intention was to investigate whether alanine and PEP might act synergistically to main a normal level of both red cell ATP and 2,3 diphosphoglycerate (2,3 DPG) under normal liquid storage conditions. Storage in the presence of alanine kept the red cell concentration of 2,3 DPG higher than the reference solution for an extended period of time, provided the initial pH was about 7.0 (37.degree.C). When the pH of the storage solution containing alanine plus PEP was lowered to facilitate the transport of PEP into the red cells, the concentration of 2,3 DPG was lowered to a rate equal to that in the reference solution. The level of ATP was also about the same as in the reference solution. The majority of the added PEP was continuously converted to 2 phosphoglycerate and 3 phosphoglycerate in the extracellular fluid. A small amount of unconverted PEP penetrated the red cell membrane when the pH went below 6.5; this occurred after 3 weeks of storge. The intracellularly located PEP, however, was not metabolized to 2,3 DPG to any significant extent within the first 6 weeks of storage. These findings indicate that PEP is not suitable as an additive for liquid storage of red cells at 4.degree.C. The combination of alanine and PEP that theoretically could be a suitable additive for liquid storage of red cells was not satisfacotry in practice.