UTILIZATION OF ACETATE AND PYRUVATE FOR THE SYNTHESIS OF‘TOTAL’,‘BOUND’AND‘FREE’ACETYLCHOLINE IN THE ELECTRIC ORGAN OF <i>TORPEDO</i>

Abstract

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.