Electron microscopic examination of lead treated L6 skeletal muscle line cells in culture.

A study has been made of the effects of lead on developing muscle using a cell culture system. When the L6 clonal cell line was treated with lead acetate in culture during the first or second day after plating (but not at later times) fusion of cells to form skeletal muscle straps was inhibited. This inhibition was not due to a general toxic effect of lead on the cells since cell division continued at a normal rate during the first 10 days of culture after lead addition. When cells were examined ultrastructurally using stereology, the only apparent effect of lead was a change in mitochondrial size and configuration. Five times as many partially condensed mitochondria were seen in lead treated cells, and mitochondrial size was also significantly increased. Lead appears to effect a very early event in cell fusion since gap junction formation (a necessary event in fusion) and some synthesis of myofibrils occur even in the presence of lead.