Molecular species of acetylcholinesterase in denervated rat skeletal muscle

Acetylcholinesterase (AChE, E.C. 3.1.1.7) activity was investigated in homogenates of control and denervated rat extensor digitorum longus muscle. Denervation produced a large, rapid decrease in AChE activity. Calculated on a whole-muscle basis, this decrease was 18% at 2 days after denervation and 75% at 7 days. NaCl (1 m), 0.5% Triton X-100 extracts of extensor digitorum longus muscle were subjected to velocity sedimentation in sucrose gradients. Three peaks of AChE activity were found with sedimentation coefficients of 3.9 S, 9.9 S, and 16.0 S. In control muscles, the distribution of AChE activity among the three peaks was 39, 39, and 14%, respectively. Two days after denervation, this distribution was greatly altered, but the sedimentation coefficients remained the same. Whereas the AChE activity associated with the 3.9 S and 16.0 S peaks was reduced, that of the 9.9 S peak was increased. The greatest quantitative loss in AChE activity was associated with the 3.9 S peak. Seven days after denervation, the AChE activity of each of the three forms was greatly reduced.