The viability of young and old baboon red cells stored in the liquid state at 4 C

Baboons were given intravenous injections of 50-70 microCi of 59Fe citrate to label young and old red cells. Blood subsequently collected from these animals was stored at 4 C in ACD, CPD, or CPDA-1 for up to 36 days. The 59Fe-labelled young and old red cells from the stored blood samples were labelled in vitro with 51Cr and 99mTc and then separated by counterflow centrifugation-elutriation into 7 fractions which differed in red cell volume. 59Fe-labelled young red cells were found in the fractions with the larger red cell volumes; 59Fe-labelled old red cells were found in the fractions with the smaller red cell volumes. 51Cr and 99mTc labelled young and old red cells in the 7 fractions in a similar manner. When salivary antigens were used to identify ABO compatible baboons, rapid removal of the donor red cells from the circulation was seen in 7 of the 15 homologous transfusions. This prompted us to assess compatibility from the survival of 51Cr-labelled donor red cells. In transfusions in which compatibility was identified from 51Cr T50 values of 8 days or greater, 24-hour posttransfusion survival values were similar for the 59Fe young and old red cells. Our data show that in vivo aging of red cells is a different process from that occurring with in vitro deterioration of red cells during liquid storage at 4 C.