Myotubes originating from single fast and slow satellite cells display similar patterns of AChE expression

Slow- and fast-contracting skeletal muscles of both rats and mice display s ignificant differences in their patterns of acetylcholinesterase (AChE) exp ression. Although neural influences are known to account for a large propor tion of these differences, intrinsic variations between fast and slow myoge nic precursor cells have been implicated. In the present study, we have cap italized on the use of Immorto transgenic mice to obtain single myogenic pr ecursor cells isolated from either slow or fast muscle fibers and determine d whether these cells generated myotubes that produced distinct patterns of AChE expression as observed in vivo between slow and fast muscles. These t wo myotube populations displayed similar cell-associated and secreted AChE enzyme activity as well as comparable levels of AChE transcripts. Both myot ube populations also expressed nearly identical molecular form profiles. By contrast, AChE activity and transcript levels were approximately two- and fivefold greater in fast skeletal muscles compared with slow ones. Together , these findings indicate that differences in AChE expression between fast and slow muscles are not due to inherent differences in myogenic precursor cells, thereby suggesting that other factors, such as innervation, play a p redominant role in establishing the distinct patterns of AChE expression in these muscle types.