Recovery of acetylcholinesterase forms in quail muscle cultures after intoxication with diisopropylfluorophosphate.

Studies of recovery of acetylcholinesterase (AChE, EC 3.1.1.7) after inhibition by organophosphates (OPs) have been hampered by the low number of in vitro systems with large collagen-tailed forms of AChE characteristic of motor end plates. Pectoral muscle cultures from Japanese quail with high levels of a large 20S form of AChE were used to study recovery of cells from acute treatment with diisopropylfluorophosphate (DFP), an irreversible AChE inhibitor. Low molecular weight AChE forms were synthesized more rapidly than the large 20S form following a 15-min treatment with 10(-4)M DFP. Most of the activities of the small forms, but only part of the activity of the 20S form, disappeared within 48 hr after cycloheximide was added to block protein synthesis. To the contrary, virtually all the activity of the 20S AChE that was newly synthesized after DFP treatment was lost within 24 hr after cycloheximide treatment. The results were generally consistent with the idea that the 20S AChE form is assembled inside the cell near to its surface and then is released to bind to its outside.