Asymmetrical loss of sialic acid from membrane glycoproteins during platelet aging

Platelet cohorts prepared from less than or equal to 24 hour old rabbit platelets were infused into myelosuppressed recipient animals and allowed to age in them. Serial withdrawals of platelets at 24 hour intervals revealed a sharp drop in total platelet N-acetylneuraminic acid. Platelet membrane proteins were double labeled by reductive methylation of free amino groups in the presence of [14C]-formaldehyde and by metaperiodate oxidation of sialic acid residues followed by reduction with [3H]-NaBH4. Senescence of platelets in vivo is associated with a disproportionate loss of metaperiodate-oxidizable residues from a glycopeptide of M.W. 45,000.