Early alteration induced by tumor promoters on chick embryo muscle cells in culture.
When differentiated, multinucleated cultured myotubes are treated with PMA (Phorbol-12-myristate-13-acetate), they display drastic morphological alterations and undergo inhibition of the expression of differentiative traits, without being induced to reenter the cell cycle. Differentiated myotubes, obtained after cytochalasin B treatment of primary chick embryo myoblast cultures, were treated with 1.6 x 10(7) M PMA for different times, labelled with 35S-methionine and different fractions of cell extracts were analysed by SDS-PAGE followed by fluorography. The data presented here indicate that PMA treatment induces in myotubes increased synthesis of a 31.000 Mr polypeptide (31 K) within 4 hr of treatment, while the inhibition of the synthesis of contractile proteins, such as myosin and actin, occurs only after 8 hr of treatment. Morphological alterations of myotubes require longer incubation with PMA (15-20 hr). The reported effects of PMA are not induced by non tumor promotor analogs of the drug, and pulse chase experiments indicate that 31 K stimulation is not the result of increased protein degradation induced by PMA. In addition the stimulation of 31K does not occur in cultured fibroblast indicating that this is a specific early response of differentiated myogenic cells preceeding the dedifferentiative effect of this tumor promotor.
D000199:Actins / Q000096:biosynthesis; D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D002642:Chick Embryo; D009124:Muscle Proteins / Q000096:biosynthesis; D009132:Muscles / Q000166:cytology / Q000187:drug effects / Q000196:embryology*; D009218:Myosins / Q000096:biosynthesis; D010704:Phorbols / Q000494:pharmacology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D000199:Actins; D009124:Muscle Proteins; D010704:Phorbols; D009218:Myosins; D013755:Tetradecanoylphorbol Acetate