Studies on the Effects of Simple Sugars on Mammalian Cells in Culture and Characterization of the Inhibition of 3T3 Fibroblasts by L-Fucose1

Studies concerning the effects of naturally occurring simple sugars on the morphology and metabolism of various mam malian cell lines further illustrate the selective effects of differ ent individual sugars on specific cell lines. Attempts to char acterize the selective effects of L-fucose on 3T3 fibroblasts showed that the marked changes in morphology and inhibition of incorporation of radioactive precursors were reversible. Also, the plating efficiency of 3T3 cells grown in medium containing L-fucose for 24 hours was not diminished. Studies of the se quence of inhibition of incorporation of radioactive precursors in fucose-containing cultures showed that uridine incorporation was decreased before leucine and thymidine. In contrast to the striking effects of L-fucose on rapidly growing cultures of 3T3 cells, the addition of this sugar to confluent cultures caused no apparent effects. The mechanisms by which L-fucose causes these changes in 3T3 cells are unknown. However, it does not appear to be caused directly by interference with the uptake or utilization of glucose. Furthermore, the selective inhibition by L-fucose appears to require very little of this sugar to be taken up by the cells. Parallelisms between the characteristics of inhibition by L-fucose and those of cell con tact inhibition of mitosis raise the possibility that similar mechanisms operate in both phenomena. Regardless of the mechanisms responsible for the selective effects of L-fucose, the results suggest that naturally occurring sugar constituents of cells may play a unique role in influencing cell growth and metabolism.