In vivo ageing of rat erythrocytes and cell surface labeling by D-galactose oxidase and sodium borotritide.

1. Young and old rat erythrocytes, separated in vitro, according to their age in vivo, were radioactively labeled at the cell surface D-galactosyl and 2-acetamido-2-deoxy-D-galactose (Gal and GalNAC) residues by treatment with D-galactose oxidase, followed by reduction with sodium borotritide: 2. The number of labeled surface residues per erythrocyte was found to be 0.52 X 10(6) +/- 0.08 X 10(6) for young, 0.38 X 10(6) +/- 0.05 X 10(6) for middle-aged and 0.32 X 10(6) +/- 0.05 X 10(6) for old, indicating a significant decrease of these surface Gal and GalNAC residues during ageing. 3. Qualitative changes were observed between the sodium dodecyl sulfate electrophoretic patterns of young, middle-aged and old labeled erythrocytes. 4. Quantitative changes were previously observed between the electrophoretic patterns of the labeled glycoproteins from young, middle-aged and old human labeled erythrocytes. 5. It is concluded that some of the changes occurring during in vivo ageing of rat and of human erythrocytes are different.