CHRONIC ENHANCEMENT OF NEUROMUSCULAR ACTIVITY INCREASES ACETYLCHOLINESTERASE GENE-EXPRESSION IN SKELETAL-MUSCLE

We determined levels of mRNA encoding acetylcholinesterase (AChE) in m uscles of rats subjected to chronic enhancement of neuromuscular activ ation. After 8 wk of voluntary wheel running, extensor digitorum longu s (EDL) muscles displayed a 72% increase in total AChE activity as a r esult of a selective threefold increase in the G(4) content. Soleus mu scles, on the other hand, exhibited a 30% decrease in A(12) while disp laying a small (33%) increase in total AChE activity. These enzymatic adaptations were paralleled by increases in the levels of AChE mRNAs i n both EDL (32%; P < 0.03) and soleus (42%; P < 0.02) muscles. In addi tion, compensatory hypertrophy of the plantaris muscle increased total AChE activity by 75%. This change was reflected by an elevation in al l AChE molecular forms with A(12) (89%) and A(8) (179%) showing the mo st prominent increases. Similar to exercise-trained muscles, hypertrop hied plantaris muscles displayed an increase in AChE transcripts (25%; P < 0.04). These results indicate that increases in neuromuscular act ivity modulate expression of the AChE gene in vivo and suggest the inv olvement of pretranslational regulatory mechanisms in the adaptive res ponse of AChE to enhanced neuromuscular activation.