The uptake of [14C]choline into synaptosomes in vitro |
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| Authors: | R. M. Marchbanks |
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| Affiliation: | Department of Biochemistry, University of Cambridge |
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| Abstract: | 1. The uptake of [(14)C]choline into synaptosomes in vitro was investigated by a gel-filtration method. Synaptosomes incubated in a medium fortified with glucose and succinate rapidly take up [(14)C]choline. 2. A substantial proportion of the radioactivity taken up can be released by osmotic shock, and is recoverable as choline on a thin-layer chromatogram. This suggests that choline is taken up across the limiting membrane into the cytoplasmic compartment of the synaptosome. 3. The concentration of choline in the synaptosome has a dependence on the external concentration of choline that is similar to that in erythrocytes and mouse cerebral-cortex slices. The choline influx has two components, one that is linear and one that is saturable with increasing choline concentration. 4. Omission of Na(+) from the incubation medium, or addition of 100mm-K(+), inhibits choline uptake. Hemicholinium no. 3 is a powerful inhibitor of the choline uptake. 5. The similarity of the choline-uptake process in synaptosomes to that in erythrocytes and cortex slices indicates that the synaptosome limiting membrane is functionally competent in this respect. |
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