Abstract
Choline esterase, present throughout the body, exists in especially high concentrations at the end plates of striated muscle, in the synapses both of the central nervous system and of the sympathetic ganglia. 1 , 2 The concentration in these 3 foci is sufficiently high to satisfy the requirements of the theory that acetylcholine (ACh) may be involved in the transmission of nerve impulses from neurone to neurone or from neurone to striated muscle fibre. The alterations in enzymatic concentration which occur after the nerve endings disappear have been investigated.
It has been found in guinea pigs that section of the sciatic nerve is followed by a rise in concentration of choline esterase in the gas-trocnemius muscle. 3 The Q. Ch. E. (mg ACh hydrolyzed per hour by 100 mg of fresh tissue) depends to a large extent on the number of end plates per unit of weight because of the high concentration of enzyme at these points. It was thought that the increase in choline esterase might be due to the decrease in volume of muscle fibers, leading to an increase in the number of fibers per unit of weight and consequently in number of end plates or more precisely “sole-plates” which persist after the nerve endings have disappeared. If the volume of fibers decreased and the Q. Ch. E. increased at the same time to the same extent it would imply that the enzyme concentration at the end plates remained practically the same.
Determinations of the volume of fibers, carried out 1-3 weeks after denervation show that the decrease fully accounts for the apparent increase of enzyme concentration. The rise of concentration actually is not quite as great as the corresponding diminution of volume.
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