Effect of sialidase on the viability of erythrocytes in circulation

Sialic acid has been detected on the erythrocyte surface of a number of different species of animals. The objective of this investigation was to determine the physiological significance of these sialyl residues to the viability of erythrocytes in circulation. Methods have been described for the determination of total sialic acid on red blood cells and the conditions under which it may be released with sialidase. Chicken, dog, goat, and rabbit were chosen for these studies because of the differences in the amount (3 X 10(6) - 72 X 10(6) resides per erythrocyte), and type (N-acetyl-or N-glycolyl-neuraminic acids) of sialic acid found on the surface of their erythrocytes. Radioactive tagging with Na251CrO4 was used to monitor the effect of sialidase on the viability of erythrocytes upon autologous transfusion. By the two criteria used to assess the viability of erythrocytes-the percentage of erythrocytes surviving 24 hr after the autologous transfusion, and the half-life of those red blood cells in circulation that survive the first 24 h after the autologous transfusion, and the half-life of those red blood cells in circulation that survive the first 24 hr-it is apparent that the presence of sialic acid on the cell surface is crucial for the survival of nonnucleated mammalian erythrocytes. The loss of viability of dog erythrocytes can be elicited by the removal of approximately 10% of the total sialic acid. In marked contrast to the behavior of mammalian erythrocytes, sialidase-treated chicken erythrocytes appear to retain their viability in circulation.