Determination of acetylcholine in human blood.

Acetylcholine levels of whole blood from 80 healthy subjects were determined by pyrolysis-gas chromatography-mass fragmentography. Acetylcholine was extracted from 1.2 ml of venous blood in the presence of eserine, demethylated by pyrolysis, and assayed by selected ion-current monitoring using butyrylcholine as an internal standard. Inhibition of blood cholinesterase activity by eserine was essential to accurate measurement. The overall recovery of acetylcholine was 45%. The blood acetylcholine levels of healthy subjects varied over a wide range with a geometric mean of 0.49 mumole/liter, 90% of the levels falling into the range of 0.20 to 1.31 mumole/liter. There was no correlation between the blood acetylcholine level and age or sex.