CHRONIC ZINC ADMINISTRATION IMPROVES ENDOTHELIAL CELL FUNCTION AND VASCULAR REACTIVITY IN EXPERIMENTALLY-INDUCED DIABETES MELLITUS IN RATS
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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 (120) 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: (I) Zinc restored plasma antioxidant defenses as it significantly (p<0.05) increased the GSH/GSSG ratio. the (TEAC) and significantly (pc0.05) decreased LPO. This resulted in lowering the quenching effect of free radicals on nitric oxide (NO). (2) Chronic zinc administration significantly (p<0.05) increased intracellular Mg2+ concentration and significantly (p<0.05) decreased intracellular Ca2" content, thus protecting against oxidative cell damage and improving smooth vascular cell relaxation respectively.