| Popis: |
Acetylcholinesterase (AChE) is responsible for the rapid hydrolysis of acetylcholine into acetic acid and choline thus allowing precise temporal control of muscle contraction. The expression of AChE in skeletal muscle is strongly influenced by both nerve-evoked electrical activity and trophic factors. In recent years however, several lines of evidence have emerged indicating that mechanical forces influence the growth and differentiation of a variety of tissues including cardiac and skeletal muscles. In the present study, we therefore tested the hypothesis that AChE expression is modulated by mechanical stimulation by using two distinct, yet complementary approaches. In a first series of experiments, primary cultures of myotubes were subjected to repeated cycles of stretch/relaxation. In a second series of experiments, we further tested our hypothesis in vivo by examining AChE expression in denervated rat hemidiaphragm muscle. Results from these studies indicate that in addition to neural activation and trophic factors, passive mechanical forces modulate the expression of AChE in skeletal muscle fibers. Since in tissue cultured myotubes tetrodotoxin did not prevent the increase in AChE expression, it appears that the effects of mechanical stimulation are independent of electrical activity and further indicates the use of an alternate signalling pathway: The results therefore show for the first time, that passive mechanical forces modulate expression of a synaptic protein in skeletal muscle fibers. As such, these results fit well with converging lines of evidence indicating that the imposition of a mechanical stimulus dramatically affects expression of several muscle genes encoding specialized contractile proteins. (Abstract shortened by UMI.) |
