Different time course of development for high-affinity choline uptake and choline acetyltransferase in the chick retina

Abstract Synthesis and storage of [3H]acetylcholine in isolated pieces of chick retina increased in two stages during embryogenesis. The first increase coincided with a 100-fold rise in the activity of choline acetyltransferase (acetyl-CoA:choline O-acetyltransferase, EC 2.3.1.6), but during the second increase the activity of this enzyme remained essentially constant. The second increase instead was linked to an approximately 6-fold increase in the Vmax for high-affinity uptake of choline.