STUDIES ON SODIUM TRANSPORT IN RAT BRAIN NERVE‐ENDING PARTICLES

Abstract

Nerve-ending particles isolated from crude mitochondrial preparations from rat brain by discontinuous Ficoll density grandient ul-tracentrifugation were shown to possess a Mg2+ and energy-dependent transport system for Na+. Ouabain or iodoacetate plus cyanide exerted an inhibitory effect on the outflux but not the influx of Na+. When K+ was added to a medium containing particles loaded with Na+ (22Na)i an immediate release of Na+ from these particles was observed; this suggests the existence of a Na+-K+ exchange transport system. The K+ effect was inhibited by 10-4 M-ouabain only at low (about 3.3 mM). but not at high (20 mM), K+ concentrations. The uptake and release of Na+ by the nerve-ending particles were found to be temperature-dependent. Only nerve-ending particles with intact synaptosomal membranes were found to transport Na+ actively.