Interactions of acetylcholine receptors with organic mercury compounds.
Micromolar concentrations of methylmercury and several organic mercury fungicides were found to block binding of [3H]acetylcholine (ACh) to the ACh-receptor of the electric organ of the electric ray, Torpedo ocellata. The same compounds had little or no effect on the catalytic activity of ACh-esterase of the same tissue. [14C]Methyl-mercury bound to the purified ACh-receptor with high affinity (Kd=7micrometer) and there were 6.5 +/- 0.5 binding sites for each ACh-binding site. Binding of methylmercury was highly cooperative with a Hill coefficient of 2.6. This binding was irreversible by redialysis in methylmercury - free medium, however, the bound [14C]methylmercury was easily displaced from the receptor protein with micrometer concentrations of BAL or penicillamine. Methylmercury also blocked binding of [3H] nicotine and [3H]pilocarpine to the nicotinic and muscarinic ACh-receptors of the rat brain, respectively. The data suggest that the ACh-receptor may be a target for methylmercury and other organic mercury compounds.
D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism / Q000648:ultrastructure; D002800:Cholinesterase Inhibitors; D004557:Electric Organ / Q000378:metabolism; D005399:Fishes; D066298:In Vitro Techniques; D007700:Kinetics; D008767:Methylmercury Compounds / Q000378:metabolism; D009538:Nicotine / Q000378:metabolism; D009941:Organomercury Compounds / Q000378:metabolism* / Q000494:pharmacology; D010862:Pilocarpine / Q000378:metabolism; D051381:Rats; D011950:Receptors, Cholinergic / Q000187:drug effects / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism
D002800:Cholinesterase Inhibitors; D008767:Methylmercury Compounds; D009941:Organomercury Compounds; D011950:Receptors, Cholinergic; D010862:Pilocarpine; D009538:Nicotine; D000109:Acetylcholine