Histochemical and biochemical observations on cholinesterases of cat's tapeworm Taenia taeniaformis

Cholinesterase activity of the tapeworm was studied histochemically with the Koelle method, using acetylthiocholine and butyrylthiocholine as substrates, and biochemically with the Warburg technique, using acetylcholine, acetyl-β-methylcholine and butyrylcholine as substrates.Eserine.tetra-isopropylpyrophosphoramide (iso-OMPA), 1,5-bis (4-trimethylammonium-phenyl-phntan-3-one diiodide (BW 62 C 47) and 1,5-bis(4-allylmethyl-ammonium-phenyl) pentan-3-one diiodide (BW 284 C 51) were used as inhibitors.Both the histochemically and the biochemically demonstrable tapeworm cholinesterase activity was readily inhibited by low concentrations of eserine but resistant to the other inhibitors employed, whatever substrate was used.In this respect the tapeworm cholinesterase activity markedly differed from that in the human serum, the rat brain homogenate or the duodenum of the cat, which were used as reference sources of cholinesterase.The histochemical cholinesterase reactions obtained with acetylthiocholine and butyrylthiocholine, with or without iso-OMPA or BW 62 C 47, showed identical distributions, selectively limited to nervous ganglia, nerve trunks and nerve fibres of the worm, including those innervating the suckers.It is concluded that the tapeworm cholinesterase is distinct from mammalian acetylcholinesterase and non-specific cholinesterase, even if it is, like acetylcholinesterase, a selectively neuronal enzyme and inhibited by excess substrate.