Sanne de Bruin

129 Metabolic changes in erythrocytes in vivo, during storage and after transfusion of the high concentration of oxygen in erythrocytes, reactive oxygen species are one of the most important stress factors in erythrocytes 27 . During increased oxidative stress young erythrocytes have a higher flux through the PPP than the oldest cell population. In contrast, when the cells are in steady state no differences in PPP flux between young and aged RBC were observed 28 . However, it is seen that in old erythrocytes the PPP related enzymes are less active, in particular G6PD 20,24,29–31 . Also, the activity of 6-phosphogluconate dehydrogenase, the enzyme responsible for the second step in the PPP, decreases but not as pronounced as G6PD 31 . Some contradictory results about the GSH levels have been published over the years. It has been described that GSH levels are higher in reticulocytes but remain constant after maturation 20,32 , while other studies have described an age dependent decrease up to 70% 20,29,33,34 . Results about glutathione disulfide (GSSG) are more consistent, GSSG is oxidized GSH, and can be reduced to GSH using NADPH. Overall, a decrease in the GSH/ GSSG ratio is seen in aged erythrocytes 29,32,34 . Metabolism during in vitro storage To minimize the storage lesion an additive solution is added to a RCC which contains RBC and a small amount of plasma. Many different additive solutions with different concentrations of various substrates exist (see table 1). Each additive solution has its own impact on the metabolic changes during storage 35 , however, the metabolism of stored RBC shows also some similarities when using the different additive solutions. Table 1. Composition different additive solutions. Ingredients (mmol/L) Additive solution SAGM AS-1 AS-3 AS-5 AS-7 PAGGGM PAGGSM NaCl 150 154 70 150 - - 72 NaHCO3 - - - - 26 - - NaH2PO4 - - 23 - - 8 8 Na2HPO4 - - - - 12 8 16 Na-gluconate - - - - - 40 - citric acid - - 2 - - - - Na-citrate - - 23 - - - - adenine 1.25 2 3 2.2 2 1.4 1.4 guanosine - - - - - 1.4 1.4 glucose(dextrose) 50 111 55 45 80 47 47 mannitol 29 41 - 45.5 55 55 55 pH 6.2 5.5 5.8 5.5 8.5 8.2 6.0 5