Rat liver contains age-regulated cytosolic 3-deoxy-D-glycero-D-galacto-non-2-ulopyranosonic acid (Kdn)

Kdn (3-deoxy-D-glycero-D-galacto-non-2-ulopyranosonic acid), a unique deami nated member of the sialic acid family, has emerged as a new building block of glycoconjugates from a wide variety of organisms, ranging from bacteria to mammals. In particular, the presence of Kdn has been demonstrated in di fferent rat organs and tissues, but not in liver. Here we report on the det ection and quantitation of Kdn in rat li, er and on its variations with pos tnatal development and aging, We have previously established the optimal co nditions for derivatization of Kdn with 1,2-diamino-4,5-methylene-dioxybenz ene (DMB), and detection by reverse-phase HPLC. Analysis of whole liver hom ogenates and different subcellular fractions reveals that Kdn is fundamenta lly present in the cytosolic fraction as nucleotide precursor. The expressi on of Kdn, NeuSGc, and Neu5Ac changes unevenly with age. While the content of Neu5Ac, the major species, and NeuSGc decreases to a different extent fr om newborn to old animals, Kdn content decreases from newborn to trace amou nts in adult rats and increases again with aging. Thus, expression of Kdn, NeuSGc, and Neu5Ac appears to be independently regulated.