Mg2+/Ca(2+)-ATPase activity is not enriched in synaptic vesicles isolated from rat cerebral cortex.
Neuronal ATPases comprise a wide variety of enzymes which are not uniformly distributed in different membrane preparations. Since purified vesicle fractions have Mg2+/Ca(2+)-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+/Ca(2+)-ATPase activities and ultrastructural studies of isolated fractions were carried out. It was observed that similar specific activities for Mg2+/Ca(2+)-ATPases were found in all fractions studied which contain synaptic vesicles and/or membranes. Although the present results confirm the presence of Mg2+ and Ca(2+)-ATPase activities in synaptic vesicles preparations, they do not favor the contention that Mg2+/Ca(2+)-ATPase is a good marker for synaptic vesicles.
Rodríguez de Lores Arnaiz
G
G
Instituto de Biología Celular y Neurociencias Prof. Eduardo De Roberts Facultad de Medicina, Universidad de Buenos Aires, Argentina.
Pellegrino de Iraldi
A
A
D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism*; D002499:Centrifugation, Density Gradient; D002540:Cerebral Cortex / Q000201:enzymology* / Q000648:ultrastructure; D005260:Female; D008297:Male; D008928:Mitochondria / Q000201:enzymology / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D013572:Synaptic Vesicles / Q000201:enzymology*
D017301:Ca(2+) Mg(2+)-ATPase