AChE mRNA stability in mammalian skeletal muscle, studied in vitro

Acetylcholinesterase (AChE) mRNA in fast rat skeletal muscle is downregulat ed by both, electromechanical activity and denervation. One candidate mecha nism that could explain decreased level of AChE mRNA in the denervated musc le is increased rate of its degradation In order to test this possibility, total deproteinated RNA was isolated from rat m SM and exposed to subcellul ar muscular fractions prepared from contralateral m.SM. After selected time intervals, we determined remaining AChE mRNA by nonradioactive Northern bl ot analysis. AChE mRNA remained at the same level during first 5 hours after denervation and abruptly fell after subsequent 13h, Further decrease in the transcript level proceeded at much slower rate Longer transcript (3.5 kb) was more af fected than the shorter (2.3 kb) one. The level of a-actin mRNA was also de creased in the denervated muscle, and the rate of its disappearance was sim ilar to that of AChE mRNA suggesting that AChE mRNA is not specifically aff ected under such conditions. Degradation of AChE mRNA was observed in all s ubcellular fractions studied. Postmitochondrial and postpolysomal fractions exibited higher rate than polysomal fraction. We find experimental approac h demonstrated here suitable for studies of degradation capacities of the s pecific mRNAs in the adult skeletal muscles. Our preliminary results sugges t, that Fail of AChE mRNA after denervation at least partly results from in creased degradation of transcripts under such conditions.