Increase in activity of acetylcholinesterase by 20-OH-ecdysone in a Chironomus tentans cell line

An epithelial cell line from Chironomus tentans exhibits acetylcholinesterase activity (specific activity 0.05-0.2 nkat/mg protein), which rises 30- to 40-fold after addition of 10^-6 M 20-OH-ecdysone. The first visible increase occurs after 4 days of incubation with hormone. The enzyme has an apparent K _m of 2.3±0.2×10^-4 M for acetylthiocholine iodide as substrate and is inhibited by eserine and BW284 C51 (50% inhibition at 5×10^-7 M for both inhibitiors) as well as by high concentrations of substrate, but not by tetraisopropylpyrophosphamide. The sensitivity against inhibitors is the same in extracts from hormone-treated cells and from controls. The cholinesterase activity correlates with morphological changes (shape and cell arrangement) and is indepenent of neuronal differentiation. We therefore propose a function for this activity during morphogenesis.