Iron-Induced Inhibition of Na+, K+-ATPase and Na+/Ca2+ Exchanger in Synaptosomes: Protection by the Pyridoindole Stobadine

The effect of oxidative stress, induced by Fe2+-EDTA system, on Na+,K+-ATPase, Na+/Ca2+ exchanger and membrane fluidity of synaptosomes was investigated. Synaptosomes isolated from gerbil whole forebrain were incubated in the presence of 200 μM FeSO4-EDTA per mg of protein at 37°C for 30 min. The oxidative insult reduced Na+,K+-ATPase activity by 50.7 ± 5.0 % and Na+/Ca2+ exchanger activity measured in potassium and choline media by 47.1 ± 7.2 % and 46.7 ± 8.6 %, respectively. Membrane fluidity was also significantly reduced as observed with the 1,6-diphenyl-1,3,5-hexatriene probe. Stobadine, a pyridoindole derivative, prevented the decrease in membrane fluidity and in Na+/Ca2+ exchanger activity. The Na+,K+-ATPase activity was only partially protected by this lipid antioxidant, indicating a more complex mechanism of inhibition of this protein. The results of the present study suggest that the Na+/Ca2+ exchanger and the Na+,K+-ATPase are involved in oxidation stress-mediated disturbances of intracellular ion homeostasis and may contribute to cell injury.