Fibre type-specific gene expression activated by chronic electrical stimulation of adult mouse skeletal muscle fibres in culture.

1. Fast-twitch skeletal muscle fibres were enzymatically dissociated from adult mouse flexor digitorum brevis (FDB) muscles and maintained in culture without or with chronic low frequency stimulation (one 5 s train of 5 Hz pulses per minute) for up to 6 days. Single fibre reverse transcriptase-polymerase chain reaction was conducted to coamplify beta-myosin heavy chain (beta-MHC) and alpha-skeletal actin mRNA from the same fibre. 2. Chronic low frequency electrical stimulation of FDB fibres in culture increased the level of mRNA for beta-MHC. In unstimulated fibres there was a slight decline in the beta-MHC mRNA level. As an internal control there was no increase in the level of mRNA for alpha-actin in the identical individual stimulated or unstimulated fibres. 3. Neither the percentage of fibres exhibiting beta-MHC protein nor the Ca2+ transients recorded from individual fibres subjected to the same pattern of stimulation showed any difference between stimulated and unstimulated fibres over the period in culture. 4. This system provides a convenient in vitro model system for studying activity-dependent control of fibre type-specific gene expression in adult skeletal muscle fibres in culture.