Susceptibility to apoptosis in different murine muscle cell lines.

Objective of the study was to investigate growth characteristics and susceptibility to apoptosis in different murine muscle cell lines (selected for high body weight, DU-6; randomly mated control, DU-Ks; immortalized myoblast cell line, C2C12). Apoptosis was induced by serum deprivation. At days 4, 5, and 6 of cultivation, protein, DNA and the frequency of apoptotic cells were determined. Until day 4, C2C12 accumulated more DNA and protein compared with DU-Ks and DU-6, while exhibiting a lower percentage of apoptotic cells. Serum deprivation impaired the growth of each cell line. C2C12 continued to accumulate DNA and protein after serum deprivation, whereas reductions, indicative of cell death, were apparent in DU-Ks and DU-6. Serum deprivation did not enhance apoptosis in C2C12. Higher percentages of apoptosis were observed in DU-Ks and DU-6 after 2 days of serum deprivation with greater responsiveness of DU-6 to serum deprivation. The results suggest that cell loss in response to serum deprivation is in part due to induction of apoptosis. C2C12 are less sensitive to sub-optimal culture conditions compared with DU-Ks and DU-6 which are at a closer distance to the in vivo status. Moreover, long-term selection for growth decreases the basic frequency of apoptosis of muscle satellite cells, but increases their susceptibility to apoptosis induction.