Nature of Placental Cholinesterase

Abstract

IN the course of a study of the types of cholinesterase occurring in different mammalian tissues, we have examined the ability of both fresh and perfused human placentas to hydrolyse acetyl choline, acetyl-β-methyl choline and benzoyl choline. Torda¹ had previously shown that perfused, blood-free placental tissue hydrolysed acetyl choline; but she did not report on the specificity of the enzyme in this tissue. Typical results which we have obtained using Mendel, Mundell and Rudney's “specific” substrates² are given in the accompanying table. Enzymic activity has been measured by the Warburg technique using homogenized preparations of fresh and perfused placentas; in the latter case, the tissue was perfused with tap-water through the umbilical vein until the effluent fluid was no longer visibly blood-stained.