Pregelj_2000_Pflugers.Arch_440_R112

The influence of mechanical load on the levels of acetylcholinesterase (AChE) mRNA was studied in order to examine to which extent different loading conditions may be responsible for differences in AChE regulation between the soleus, which is an antigravity muscle, and the fast EDL muscle. Forty-eight female rats were randomly assigned to three groups: a group with hindlimb suspension producing soleus muscle unloading, a group with ablation of synergistic gastrocnemius muscle causing overload of the soleus muscle, and the control group. The soleus muscles were isolated after 8 days of treatment AChE mRNA levels were analyzed by Northern blots and evaluated densitometrically. The values were normalized with beta-actin mRNA level, and then a value of 100% was assigned to the mRNA level in the control EDL muscle. Muscle unloading did not produce a significant increase of the AChE transcript levels, but the levels were rather variable. However, a statistically significant increase of AChE mRNA levels was observed in overloaded soleus muscles. These results corroborate the hypothesis that the slow and fast patterns of activity appear more important then muscle loading for the differences in regulation of AChE mRNA levels in fast and slow muscles.