Distribution of sodium-plus-potassium-stimulated adenosine-triphosphatase activity in isolated nerve-ending particles

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Abstract
A rapid method for the isolation of nerve-ending particles from [guinea pig] brain is described. This involved the centrifugation of the large-granule fraction over a discontinuous density gradient consisting of 3% (w/v) and 13% (w/v) Ficoll disolved in 0.32 [image]-sucrose. The results of the biochemical as well as morphological identification of nerve-ending particles are given. Approx. 20% of the (Na+ + K+)-stimulated adenosine-triphosphatase activity originally present in the cerebral grey-matter suspension was recovered in the fraction consisting principally of large nerve-ending particles (approx. 1 [mu] in diameter). The activity of the adenosine-triphosphatase/mg of protein in the nerve-ending fraction approximated to that in the small-granule fraction after the treatment with glycol ether diaminetetra-acetic acid. The conclusion was drawn that the synaptic structure, supposedly the limiting membrane of the nerve-ending particle, is one of the feasible sites of localization of the (Na+ + K+)-stimulated adenosine-triphosphatase activity in cerebral tissues. Adenosine triphosphatase in purified cerebral mitochondria was not stimulated by Na+. No qualitative differences were found between the (Na+ + K+)-stimulated adenosine-triphosphatase activities exhibited by the nerve-ending particles and by the cerebral small-granule fraction with respect to pH-dependence, cation requirements and susceptibility to ouabain.