Mg2+ /Ca2+-ATPase activity is not enriched in synaptic vesicles isolated from rat cerebral cortex

G. RODRÍGUEZ DE LORES ARNAIZ; A. PELLEGRINO DE IRALDI

NEUROCHEMICAL RESEARCH

SPRINGER/PLENUM PUBLISHERS

Año: 1997 vol. 22 p. 293 - 296

0364-3190

Neuronal ATPases comprise a wide variety of enzymes which are not uniformly distributed in different membrane preparations. Since purified vesicle fractions have Mg2+/Ca2+-ATPase, the purpose of the present study was to know whether such enzyme activities have a preferential concentration in a synaptic vesicle fraction in order to be used as markers for these organelles. Resorting to a procedure developed in this Institute, we fractionated the rat cerebral cortex by differential centrifugation following osmotic shock of a crude mitochondrial fraction and separated a purified synaptic vesicle fraction over discontinuous sucrose gradients. Mg2+/Ca2+-ATPase activities and ultrastructural studies of isolated fractions were carried out. It was observed that similar specific activities for Mg2+/Ca2+-ATPases were found in all fractions studied which contain synaptic vesicles and/or membranes. Although the present results confirm the presence of Mg2+ and Ca2+-ATPase activities in synaptic vesicles preparations, they do not favor the contention that Mg2+/Ca2+-ATPase is a good marker for synaptic vesicles.