Triton detergents and the frog neuromuscular end-plate: an electrophysiological and ultrastructural study.
The effects of the nonionic detergents Triton X-45 and Triton X-100 were studied in the frog muscle end-plate, by intracellular recordings of spontaneous miniature end-plate potentials (m.e.p.p.'s) and the potential changes produced by iontophoretic application of acetylcholine (ACh-potentials). In addition, the ultrastructural changes produced by Triton X-100 were studied by transmission electron microscopic and freeze-fracture techniques. It was found that Triton X-45 and Triton X-100 caused a rapidly developing reduction of the amplitude of the m.e.p.p.'s. The response to iontophoretic application of acetylcholine was reduced by Triton X-100. Following return to normal Ringer solution the ACh-potentials recovered, although not completely. The dissociation constant calculated from the rate constants for onset and offset of the reaction (Kp=k2/k1) was 5--50 micron depending on the type of stoichiometric reaction presumed to occur between Triton X-100 and the cholinergic receptor. The ultrastructural changes observed indicate that the nerve terminal plasma membrane and mitochondria are affected by Triton X-100. Leakage of Ca2+ from the latter may therefore be the cause of the increase in m.e.p.p. frequency. It is concluded that the influence on the amplitude of the m.e.p.p.'s and the ACh-potentials can be attributed to a direct effect of the detergent upon the acetylcholine receptor protein.
D000109:Acetylcholine / Q000502:physiology; D000818:Animals; D004285:Dogs; D005614:Freeze Fracturing; D008564:Membrane Potentials / Q000187:drug effects; D008854:Microscopy, Electron; D009045:Motor Endplate / Q000187:drug effects* / Q000648:ultrastructure; D009132:Muscles / Q000294:innervation / Q000648:ultrastructure; D009469:Neuromuscular Junction / Q000187:drug effects*; D011092:Polyethylene Glycols / Q000494:pharmacology*; D011896:Rana temporaria; D013570:Synaptic Membranes / Q000648:ultrastructure; D013572:Synaptic Vesicles / Q000648:ultrastructure
D011092:Polyethylene Glycols; D000109:Acetylcholine