20-OH-ECDYSONE-INDUCED MORPHOGENETIC MOVEMENTS IN A CHIRONOMUS CELL-LINE ARE ACCOMPANIED BY EXPRESSION OF AN EMBRYONIC MUSCARINIC SYSTEM

The permanent epithelial insect cell line used was derived from Chiron omus tentans embryos. Cells are maintained in suspension culture, wher e they grow as single-layered vesicles. On treatment with the moulting hormone 20-OH-ecdysone cell division ceases. Patches of cuboidal epit helium appear in the vesicles which finally become multilayered and fo rm bud-like protrusions at the outside. In the present study, we local ized cholinesterase activity in the cell protrusions by histochemistry and demonstrated coexpression of cholinergic muscarinic receptors by immunofluorescence. Muscarinic receptors were visualized with the mono clonal antibody M35. Six hours after treatment with 20-OH-ecdysone, mu scarinic receptors appeared in a few individual cells of the epithelia l vesicles before morphological changes became visible. After 24 h, im munofluorescence was concentrated in multilayered patches which now al so showed cholinesterase activity, After 3 days, muscarinic receptors and cholinesterase activity were localized in the epithelium protrusio ns. The results are discussed in the context of an embryonic cholinerg ic muscarinic system the expression of which has been described in ver tebrate and non-vertebrate embryos and is correlated with phases of mo rphogenesis.