Post-transfusion survival of 50Cr-labeled erythrocytes in neonatal foals.

Erythrocytes transfused allogeneically into mature horses have a short survival (less than 4 days) compared with an expected erythrocyte life span of 140-150 days. Yet, foals undergo transfusions for neonatal isoerythrolysis successfully. The authors have determined the survival of transfused erythrocytes in neonatal foals, using the stable isotope, 50Cr, to label the erythrocytes. Normal foals underwent transfusions with labeled erythrocytes from three sources: their own erythrocytes (autologous), the erythrocytes of their dam, and the erythrocytes of an unrelated castrated male. After transfusion, samples were taken at 15 minutes and then daily for a week and every 2 or 3 days for 20 days. A stable isotope of iron (57Fe) and 50Cr were determined on diluted-packed erythrocytes by inductively coupled argon-coupled mass spectrometry techniques. 57Fe was used as measure of the sample hemoglobin concentration. The ratio of 50Cr to 57Fe decreased exponentially in all foals. Half-time (T1/2) was 11.7 days (standard error = 2.2) for four foals that underwent autologous transfusions, 5.5 +/- 1.0 days for five foals that underwent transfusions with the erythrocytes of their dams, and 5.2 +/- 1.1 days for five foals that had transfusions with erythrocytes from an unrelated gelding. The authors conclude that erythrocytes that are transfused allogenically into neonatal foals will survive longer than those transfused into mature horses and that 50Cr labeling can be used to measure survival of transfused erythrocytes.