Rate of Formation of Acetylcholine in Placenta In Vitro

Abstract

We have demonstrated that placental acetylcholine originates in the syncitial layer of the villus, and that it exists in a free form. 1 We now have evidence that it also exists in a reserve form. The former can be readily extracted by alcohol, and quite satisfactorily by saline, providing precaution is taken to prevent the activity of cholinesterase with sufficient eserine and handling at ice-cold temperature. The latter appears to be liberated on incubation of the placenta at a favorable temperature, viz., 37°C. The present report deals with the rate of liberation of this reserve acetylcholine from its precursor in vitro.

Five experiments have given similar results, one of which will be briefly presented. In this particular experiment, a placenta which was freed from its foetal membrane and cord was minced and divided into 18 lots each weighing 20 gm. Three series of observations were carried out, one with eserine represented by EC, E11, E12, E13, E14, and E15, and 2 without designated by C, 11, 12, 13, 14, 15 and C′ 11′, 12′, 13′, 14′, 15′; each series thus consisted of 6 samples. Three cc. eserine solution (25 mg. eserine salicylate) were added to each sample of the eserine series, while 3 cc. saline were added to each of the non-eserine series before starting the experiment. The control samples of the 3 series were immediately extracted for their free acetylcholine with 2 volumes of 96% alcohol in the ice chest for 17.5 hours. The rest were incubated at 37°C., one sample from each series being removed at hourly intervals for similar extraction of the same duration. At the end of extraction, the tissues were squeezed through gauze, the weight of residue being taken and the filtrate refiltered and measured before storage on ice.