The relative distribution of soluble and insoluble cholinesterases in rat excitable tissues.

Three ratios were studied here: bound to free AChE (R1), bound to free BChE (R2), and the ratios between these two (R3). The first one proved relevant in that it contributed to the division of the cholinergic tissues into 3 classes: high values (nicotinic tissues: skeletal muscle), low values (muscarinic tissues: small intestine, uterus, heart), and middle values (mixed, nicotinic and muscarinic cholinergic innervation: brain). The third ratio (R3) showed different values in the muscarinic tissues studied; no significant differences could, however, be found between the ratios of brain and skeletal muscle. Further exploration of this ratio should indicate whether it is of some importance for the characterization of excitable tissues.