The development and distribution of cholinesterases in cultured skeletal muscle with and without nerve

Cholinesterase development was studied biochemically and histochemically in monolayer cultures of muscle cells from 10 day chick embryo leg muscle. Cholinesterase activity was low in myoblasts but increased rapidly after cell fusion and myotube formation; activity was distributed unevenly throughout myotubes, older fibres having some small areas of intense activity. Total Cholinesterase activity increased over the 10 day culture period while soluble activity reached a plateau after 4 days and was between 30–40% of the total. Butyrylcholines-terase activity did not change significantly during the period of study, comprising about 12% of the total Cholinesterase activity at 10 days. The possible effects on Cholinesterase development of combining muscle with dissociated spinal cord cells and with spinal cord explants, and of growing muscle in medium from which non-specific neural factors had been removed, was examined. No evidence was found for a nerve trophic effect on the amount or on the localization of muscle Cholinesterases.