LACTATE DEHYDROGENASE AS A CYTOPLASMIC MARKER IN BRAIN

Abstract

Previous conclusions on the distribution of succinate dehydrogenase, lactate dehydrogenase and bound acetyl-choline in subcellular fractions of brain tissue have been confirmed by parallel studies in guinea pig tissue. Bound acetylcholine and lactate dehydrogenase were similarly distributed in density-gradient separations, and were located in the regions shown previously to contain the majority of the nerve-ending particles of the homogenate. Their location was clearly different from that of succinate dehydrogenase. Repeated freezing and thawing liberated slightly more and treatment of the washed particles with sucrose hypo-osmotic with respect to plasma liberated considerably more lactate dehydrogenase than acetylcholine. The results support the concept that acetylcholine and lactate dehydrogenase are both contained within the same nerve-ending particles, and that there is a further barrier within these particles that provides an extra hindrance to the release of acetylcholine; this barrier may be the membrane of the synaptic vesicles.