Regeneration of sialic acid on the surface of Chinese hamster cells in culture. II. Incorporation of radioactivity from glucosamine-1-14C

Cultured Chinese hamster cells incorporated radioactivity from glucosamine-1-¹⁴C into surface sialic acid and into trypsin-removable material distinct from the surface sialoglycans. Cells prelabeled with glucosamine-1-¹⁴C and then transferred to medium containing unlabeled glucosamine progressively lost counts to the medium for many hours. Such chase experiments suggested a more rapid turnover of trypsinremovable material than of surface-bound sialic acid. Further studies of the regeneration of surface sialic acid showed that the actinomycin D-resistant portion of the process involved emergence of an intracellular precursor onto the cell surface. An earlier portion of the process was inhibited by actinomycin D, and at least three steps were inhibited by puromycin or cycloheximide.