Hydrolysis of Acetylcholine by Frog Skeletal Muscle

Abstract

There are several reports showing that intact muscles hydrolyze acetylcholine (ACh) at a much slower rate than their homogenates (see for instance Refs. 4,9,10,16). Marnay and Nachmansohn (10) suggested that in intact muscle the relative slowness of the hydrolysis of added ACh by Cholinesterase (ChE) is caused by slow diffusion of ACh through the muscle tissue. In mammalian muscle the difference in ChE activity between intact and homogenized preparations has been attributed, in part or fully, to the liberation of intracellular ChE by the homogenization. This and other considerations led to the suggestion that the data obtained with intact preparations are more relevant to the physiological function of the enzyme at the endplates than those obtained with homogenates (9,16). On the other hand, it could be that the in situ synaptic activity of ChE, the “functional activity,” of the enzyme, is severely distorted by hindred diffusion, when it is measured with exogenous substrates on intact tissue.