Zinc-Excess Intake Causes the Deterioration of Renal Function Accompanied by an Elevation in Systemic Blood Pressure Primarily Through Superoxide Radical-Induced Oxidative Stress

• Published in: International journal of toxicology 2014-07, Vol.33 (4), p.288-296
• Main Authors: Yanagisawa, Hiroyuki, Miyazaki, Takashi, Nodera, Makoto, Miyajima, Yuka, Suzuki, Takashi, Kido, Takamasa, Suka, Machi
• Format: Article
• Language: English
• Subjects: Animals; Aorta, Thoracic; Biomarkers - blood; Biomarkers - metabolism; Biomarkers - urine; Deoxyguanosine - analogs & derivatives; Deoxyguanosine - metabolism; Dietary Supplements - poisoning; Endothelium, Vascular - drug effects; Endothelium, Vascular - metabolism; Endothelium, Vascular - physiopathology; Enzyme Inhibitors - adverse effects; Free Radical Scavengers - therapeutic use; Heavy Metal Poisoning - drug therapy; Heavy Metal Poisoning - metabolism; Heavy Metal Poisoning - pathology; Heavy Metal Poisoning - physiopathology; Hypertension, Renovascular - etiology; Hypertension, Renovascular - physiopathology; Hypertension, Renovascular - prevention & control; Inulin - blood; Inulin - pharmacokinetics; Inulin - urine; Kidney - blood supply; Kidney - drug effects; Kidney - pathology; Kidney - physiopathology; Male; Metabolic Clearance Rate - drug effects; Nitric Oxide Synthase - antagonists & inhibitors; Nitric Oxide Synthase - metabolism; Oxidative Stress - drug effects; Random Allocation; Rats, Sprague-Dawley; Renal Insufficiency - etiology; Renal Insufficiency - physiopathology; Renal Insufficiency - prevention & control; Superoxide Dismutase-1 - antagonists & inhibitors; Superoxide Dismutase-1 - metabolism; Zinc - poisoning
• ISSN: 1091-5818; 1092-874X
• DOI: 10.1177/1091581814532958

Using rats fed 22 g/d of a control diet containing 0.005% zinc (Zn) or 2 Zn-excess diets containing 0.05% or 0.2% Zn for 4 weeks, we examined the mechanisms involved in the deterioration of renal function induced by Zn-excess intake. An increase in Zn intake elevated mean blood pressure (BP) and reduced renal blood flow (RBF) and inulin clearance in a dose-dependent manner. This decline in inulin clearance may be derived from a fall in RBF. Administration of the nitric oxide (NO) synthase inhibitor, Nω-nitro-l-arginine methyl ester, markedly increased mean BP and significantly decreased RBF in the 3 groups of rats. Administration of the exogenous superoxide radical (OO−) scavenger, tempol, significantly decreased mean BP and substantially increased RBF in all groups of rats. These observations suggest that both an elevation in systemic BP and a reduction in RBF seen in the 2 Zn-excess diet groups result from a decrease in the action of the vasodilator, NO, through the formation of peroxynitrite based on the nonenzymatic reaction of NO and increased OO−. Indeed, the activity of the endogenous OO− scavenger, copper/Zn-superoxide dismutase, was significantly reduced in the vessel wall of rats fed 2 Zn-excess diets versus a control diet. 8-Hydroxy-2′-deoxyguanosine formation caused by OO− generation was notably elevated in the kidneys of rats fed 2 Zn-excess diets relatively to rats fed a control diet. Thus, Zn-excess intake leads to the aggravation of renal function concomitantly with an increase in systemic BP predominantly through the oxidative stress caused by OO−.