LOCALIZATION OF CHOLINE-ACETYLTRANSFERASE AND ACETYLCHOLINE IN THE CHORION OF EARLY HUMAN-PREGNANCY

This report concerns the activity of choline acetyltransferase (ChAT), and the localization of ChAT and acetylcholine (ACh) in the human cho rion during the 5th to 10th weeks of gestation. Radio-enzyme, immunohi stochemical, and in situ hybridization assays were used. We found that ChAT activity increases as a function of gestational age between the 5th and the 9th weeks of pregnancy. At 5 weeks' gestation, ChAT was de tected by immunohistochemical means mainly in cytotrophoblast and vill ous stromal cells, particularly in the cytotrophoblastic shell and cel l columns. With the development of blood vessels at the 6th week, thei r endothelial cells also expressed ChAT The amount of ChAT immunoreact ion product deposits decreased in the villous cytotrophoblast by the 9 th and 10th weeks when the layer of the cell became flat. By compariso n, ChAT protein was detected only rarely in the syncytiotrophoblast la yer during the gestation period studied. The ChAT gene transcript was demonstrated in most of the constitutive cells of the chorion. However , in contrast to the results of the immunohistochemical assays, positi ve hybridization signals for ChAT mRNA were evenly distributed over bo th cytotrophoblast and syncytiotrophoblast. On the other hand, the dis tribution of ACh immunoreaction products was almost coincident with th at of ChAT.