Quantitative changes in cholinesterase activity of denervated muscle fibers and sole plates

Abstract

Histochemical studies have indicated that normal muscle fibers exhibit little cholinesterase activity at regions other than the sole plate and that denervated muscle fibers manifest no decreased activity within 2 to 4 weeks. Because histochemical data may be quantitatively unreliable, it was decided to reinvestigate the distribution of cholinesterase with a microchemical modification of Ellman's quantitative cholinesterase method. Alternate frozen cross section (28 μ) from muscle stretched to constant length were examined histochemically and quantitatively. By counting the number of sole plates in the histochemical preparations it was possible to estimate the relative contributions of the sole-plate and the nonsole-plate tissue to the cholinesterase activity of the adjacent quantitatively analyzed tissue slice. Following denervation the sole-plate and non-sole-plate activity both decreased rapidly, reaching approximately 50 per cent of normal within 1 week. A very small additional loss in activity occurred during the following 7 weeks. The total protein content of the tissue slices declined more gradually, reaching 50 per cent of normal after 3 weeks. It is concluded that there is considerable cholinesterase activity not associated with sole plates and that denervation produces a very rapid decrease in cholinesterase activity. The neural influence on cholinesterase level is fairly specific inasmuch as denervation produces a more rapid decrease in cholinesterase activity than in total protein content whereas tenotomy produces less of a decrease in cholinesterase activity than in total protein content of the muscle.