Synthesis of deuterium- or tritium-labeled acetylcholine

Abstract

Halogenated acetylcholine precursors were synthesized. The prepared deuterium analogs of acetylcholine were characterized by HPLC and mass spectrometry. Uniformly tritium-labeled acetylcholine with the radiochemical purity of no less than 97–98% and molar radioactivity of 20–40 Ci mmol^–1 was prepared at 190°С on a Lindlar catalyst. The molar radioactivity of [³H]acetylcholine allows using it for evaluating the specific binding on plasmatic membranes of striatum cells of intact rats by radioligand–receptor binding assay. Two sites of specific binding of acetylcholine, high-affinity (binding constant K_d = 12 nmol L^–1, possible number of radioligand specific binding sites B_max = 3 pmol mg^–1) and low-affinity (binding constant K_d = 72 nmol L^–1, possible number of radioligand specific binding sites B_max = 13 pmol mg^–1), were characterized.