Choline ester formation in, and choline esterase activities of, tissues in vitro

Publisher Website
Google Scholar
Abstract
Brain cortex slices, when allowed to respire in a medium containing eserine, formed a substance which produced a powerful contraction of an eserinised leech muscle preparation. The substance was only formed in the presence of eserine, was unstable in dilute alkaline solution and its effect on the leech muscle was counteracted, like that of acetylcholine, by the presence of morphine. It is considered to be a choline ester. The choline ester was formed as a result of metabolic processes in the tissue slices, only a small fraction of it being due to preformed ester within the tissue. Under anaerobic conditions, or under aerobic conditions in the presence of cyanide, the rate of choline ester formation fell to a very low level. Oxygen was necessary for its maintenance at a high level. The presence of glucose greatly increased the rate of choline ester formation in phosphate or bicarbonate media when K and Ca ions were absent. Addition of K and Ca ions decreased the rate in a bicarbonate-glucose medium and increased it in a phosphate-glucose medium. It is suggested that there is a direct link between glucose metabolism and choline ester metabolism in tissue slices. The presence of Na lactate, pyruvate, [alpha]-glycerophosphate or glutamate increased the rate of choline ester formation but their effects were not as great as those of glucose. The rate was not increased by the presence of Na suc-cinate. Addition of NaF did not diminish the rate in a glucose medium. Addition of choline did not measurably increase the rate, nor did the presence of a large excess of acetate ions markedly increase it. Kidney, liver, spleen or testis had no measurable activity in forming choline ester under conditions most favorable for its production from brain; rat diaphragm had about i the activity of rat brain. Choline esterase activities of brain, liver, kidney, spleen, testis and defibrinated blood were recorded. There was no correlation between the choline esterase of an organ and its power of producing choline ester in vitro.