Growth of mammalian cells in the absence of the accumulation of spermine.

Mammalian spermine synthase activity was strongly inhibited by S-methyl-5'-methylthioadenosine. This nucleoside was readily taken up by SV-3T3 cells and blocked the synthesis of spermine by these cells. However, there was a corresponding increase in spermidine content and there was no effect on cell growth. These results indicate that S-methyl-5'-methylthioadenosine should be a useful compound to evaluate the role of spermine in mammalian cell physiology and that in at least one cell line the synthesis of spermine is not required for a normal growth rate.