Mar 1, 1966
Comparative biochemistry and physiology
Abstract 1. 1. Seventy per cent or more of the acetylcholine and 5-hydroxytryptamine in Mercenaria ganglia is bound to particles which sediment when homogenates of this tissue, prepared in 1·1 M glucose, are centrifuged at high speed. 2. 2. Similarly, a large proportion of the unidentified cardio-excitatory factor, Substance X, is particle bound in Mercenaria ganglia. 3. 3. Particles binding each of these substances have been partially separated from each other by density gradient centrifugation. The acetylcholine particles were mainly associated with the least dense layers of the gradient, 5-hydroxytryptamine with more dense layers and Substance X with layers of intermediate density. 4. 4. A fraction of 5-hydroxytryptamine particles has been purified twenty times over the original homogenate. The level of acetylcholine contamination of this fraction, if any, was below the limit of detection. 5. 5. Particles binding acetylcholine and 5-hydroxytryptamine release their active substances in a quantitatively similar manner to changes in pH, hypotonicity and increased temperature.