Protective mechanisms of Mg-gluconate against oxidative endothelial cytotoxicity

The potential anti-radical properties and cytoprotective effects of Mg-gluc onate were studied. When microsomal membranes were peroxidized by a O-2(-) driven, Fe-catalyzed oxy-radical system (R dihydroxyfumarate + Fe2+), Mg-gl uconate inhibited lipid peroxidation (TBARS formation) in a concentration-d ependent manner with IC50 being 2.3 mM. For the entire range of .25-2 mM, M gSO4 or MgCl2 were less than or equal to 20% effective compared to Mg-gluco nate. When cultured bovine aortic endothelial cells were incubated with the R for 50 min. at 37 degreesC, 56% loss of total glutathione occurred. Pre- treatment (10 min.) of the cells with 0.25-4 mM Mg-gluconate before R expos ure significantly (p <0.05) prevented the GSH loss to varying degrees; the EC50 was 1.1 mM. In separate experiments, with 30 min. of free radical incu bation of endothelial monolayers (-65% confluent), cell survival/proliferat ion determined by the tetrazolium salt MTT assay, decreased to 38% of contr ol at 24 hrs; Mg-gluconate concentration-dependently attenuated the lost ce ll survival with EC50 of -1.3 mM. For comparison, the effects provided by M gSO4 or MgCl2 were significantly lower and were less than or equal to1/3 as potent as that produced by Mg-gluconate. In a Fenton-reaction system consi sting of Fe(II)+ H2O2, Mg-gluconate but not other Mg-salts, significantly i nhibited the formation of OH radicals as determined by the ESR DMPO-OH sign al intensity. Mg gluconate also dose-dependently inhibited the 'Fe-catalyze d' deoxyribose degradation suggesting that Mg-gluconate could displace Fe f rom 'catalytic sites' of oxidative damage. These data suggest that Mg-gluco nate may serve as a more advantageous Mg-salt for clinical use due to its a dditional anti-radical and cytoprotective activities.