Chronic zinc administration improves endothelial cell function and vascular reactivity in experimentally induced diabetes mellitus in rats

An exaggerated oxidative stress has been postulated as the link between diabetes mellitus [D.M] and endothelial dysfunction. This study aimed to investigate the possible therapeutic effect of chronic zinc administration [0.5% in drinking water] on renal artery vascular reactivity and oxidative stress indices viz serum oxidized to reduced glutathione ratio [GSH/GSSG], trolox equivalent antioxidant capacity [TEAC] and lipohydroperoxides [LPO] in experimentally-induced D.M by streptozotocin [STZ] [60 mg/kg i.p single dose] in rats. Using Doppler technique in this study indicated that chronic zinc administration significantly [p<0.05] improved renal artery vascular reactivity to acetylcholine [Ach]. Such an effect which seemed to be mediated by two mechanisms: [1] Zinc restored plasma antioxidant defenses as it significantly [p<0.05] increased the GSH/GSSG ratio, the [TEAC] and significantly [Sp<0,05] decreased LPO. This resulted in lowering the quenching effect of free radicals on nitric oxide [NO] [2] Chronic zinc administrarion significantly [p<0.05] increased intracelular Mg 2+ concentration and significantly [p<0.05] decreased intracellular Ca 2+ content, thus protecting against oxidative cell damage and improving smooth vascular cell relaxation respectively