endobain E, An endogenous Na+, K+-ATPase inhibitor, and ascorbic acid enhance neurotransmitter release from cerebral cortex synaptosomes

M. G. BERSIER; C. PEÑA; G. RODRÍGUEZ DE LORES ARNAIZ

Nueva York, EE.UU.

Congreso; XXXV Congreso de la Sociedad Americana de Neuroquímica (ASN); 2004

Sociedad Americana de Neuroquímica (ASN)

endobain E, An endogenous Na+, K+-ATPase inhibitor, and ascorbic acid enhance neurotransmitter release from cerebral cortex synaptosomes Bersier M. G., Peña C. and Rodríguez de Lores Arnaiz G. Inst. de Biol. Cel. y Neuroc. “Prof. E. De Robertis”, Fac. Med., Cát. de Farmacol.  and IQUIFIB-CONICET, Fac. Farm.  y Bioq., UBA, Paraguay 2155, 1121 Buenos Aires, Argentina. E-mail: grodrig@ffyb.uba.ar The isolation of a soluble brain fraction which behaves as an endogenous ouabain-like substance, termed endobain E, has been described. Endobain E contains two Na+, K+-ATPase inhibitors, one of them identical to ascorbic acid. Neurotransmitter release in the presence of endobain E and ascorbic acid was studied in non-depolarizing (0 KCl) and depolarizing (40 mM KCl) conditions. Synaptosomes were isolated from cerebral cortex of male Wistar rats by differential centrifugation and Percoll gradient. Synaptosomes were preincubated in HEPES-saline buffer with 1 mM D-[3H]aspartate (15 min at 37°), centrifuged, washed, incubated in presence of additions (60 sec at 37°) and spun down; radioactivity in the supernatants was quantified. In the presence of 0.5-5 mM ascorbic acid D-[3H]aspartate release was roughly 110-150% or 135-180%, in the absence or presence of 40 mM KCl, respectively. In the presence of endobain E D-[3H]aspartate release was roughly 200-750% or 250-1100% in the absence or presence of 40 mM KCl, respectively. It is concluded that endobain E and ascorbic acid, one of its components, due to their ability to inhibit Na+, K+-ATPase, may well modulate neurotransmitter release at synapses.