Studies concerning the effects of naturally occurring simple sugars on the morphology and metabolism of various mammalian cell lines further illustrate the selective effects of different individual sugars on specific cell lines. Attempts to characterize 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 sequence 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 contact 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.
Supported by Research Contract U-1296 of the Health Research Council of the City of New York, and Grants 5 R01 HE-09239, 1 R01 GM15508-01, and FR-5399 of the USPHS.