Journal of cellular physiology
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The role of polyamines in myoblast proliferation was studied by treating cells of Yaffe's L6 line of rat myoblasts with inhibitors of polyamine synthesis. Both an irreversible inhibitor of ornithine decarboxylase--difluoromethyl-ornithine (DFMO)--and a competitive inhibitor of S-adenosyl-methionine decarboxylase--methylglyoxal-bis(guanylhydrazone) (MGBG)--depressed spermidine levels and inhibited myoblast proliferation. Spermine levels were not significantly depressed by either inhibitor and putrescine levels were decreased only by DFMO. ⋯ Unexpectedly, addition of spermidine also increased intracellular putrescine levels; this apparently resulted from conversion of spermidine to putrescine. Addition of putrescine or spermidine in the absence of serum did not increase the rate of myoblast proliferation although it did elevate intracellular polyamine levels as expected. We conclude that some threshold level of one or more polyamines (probably spermidine) is necessary but not sufficient for initiation and maintenance of myoblast proliferation in culture.