Utilization of Acetate and Pyruvate for the Synthesis Of‘total’,‘bound’and‘free’acetylcholine in the Electric Organ of Torpedo

Abstract —Slices of tissue of the electric organ of Torpedo marmorata were incubated in vitro in a salineurea‐sucrose solution containing a labelled precursor of the acetyl moiety of ACh ([1‐ 14 C]glucose, [2‐ 14 C]pyruvate, or [1‐ 14 C]acetate) either alone or in the presence of another unlabelled precursor. The incorporation of 14 C from [1‐ 14 C]acetate into ACh was considerably higher than from the other two substrates. The specific radioactivities (SRA) of the‘total',‘bound’and‘free’ACh were compared in experiments with [2‐ 14 C]pyruvate and [1‐ 14 C]acetate. With both precursors, the SRA of the‘bound’ACh were lower than those of‘total’ACh; consequently, the‘free’ACh pool was more labelled than the‘bound’pool. After short incubations with [2‐ 14 C]pyruvate the SRA of'bound’ACh were closer to the SRA of‘total’ACh than with [1‐ 14 C]acetate. A simple method is described for the labelling of ACh and its separation from other labelled compounds in experiments with the electric organ using [ 14 C]acetate as the labelled precursor.