CHANGES OF FREE LONG-CHAIN BASES IN NEURONAL CELLS DURING DIFFERENTIATION AND AGING IN CULTURE

Changes in the free long-chain base (LCB) composition in rat cerebella r granule cells in culture were studied during differentiation and agi ng. The total LCB mixtures, extracted from the cells maintained in cul ture up to 22 days, were derivatized with o-phthalaldehyde and fractio nated by reversed-phase HPLC, and each LCB species was quantified. Fou r main LCBs were components of the total LCB mixtures of cultured cell s: C18-sphingosine, C18-sphinganine, C20-sphingosine, and C20-sphingan ine. They were found in all the cells analyzed, from 0 to 22 days of c ulture, with their contents being in the sequence C18-sphingosine >C18 -sphinganine >C20-sphingosine >C20-sphinganine and varying from 0.02+/ -0.015 pmol/mg of cell protein for C20-sphinganine at day 0 to 223+/-2 2 pmol/mg of cell protein for C18-sphingosine at day 8. Sphinganines w ere found to be minor components of the total LCB mixture, with C20-sp hinganine being particularly scarce in nondifferentiated cells. The ce ll content of C20-sphinganine progressively increased from day 0 to 22 of culture; that of C18-sphinganine increased up to day 8, when cells are differentiated, and then remained quite constant. The changes of C18- and C20-sphingosine levels during cell culture were qualitatively similar to those of C18- and C20-sphinganine, but the content of the sphingosines was much higher than that of the sphinganines.