Acetylcholine in human placenta. Identification by pyrolysis gas chromatography/mass spectrometry and tissue levels following different modes of delivery.

Extracts from human term placentae were analyzed by pyrolysis gas chromatography (GC) combined with mass spectrometry. The only choline ester of carbonic acid whose presence could be unequivocally established was acetylcholine (ACh). The mass spectrum of its demethylated tertiary derivative dimethylaminoethyl acetate (nor-ACh) agreed entirely with that of authentic pyrolyzed ACh. The concentrations of ACh were determined in placentae obtained after vaginal or Caesarean delivery to investigate the claim that the latter resulted in tissue with higher concentrations of ACh-like activity presumably because ACh was not expended during labor and delivery. No differences inACh content were found with GC analysis. The ACh concentrations were 102 +/- 17 (n=8) nmoles/g fresh tissue (vaginal delivery) vs. 105 +/- 16 (n=6) nmoles/g (Caesarean section). The fetal membranes (amnion and chorion) and the umbilical cord contained no ACh under the analytical conditions with a limit of sensitivity of 200 pmoles ACh.