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The Effect of High Salt Dietary Intake and Angiotensin II Infusion on Activity of Antioxidative Enzymes in Serum of Sprague-Dawley Rats

Objective: The renin-angiotensin-aldosterone system (RAAS) regulates blood pressure, fluid volume and sodium-potassium balance, thus being one of the most important hormonal mechanisms in controlling hemodynamic stability. The systemic RAAS is under a heavy influence of dietary salt intake and is suppressed by a highsalt diet. In addition, previously, we (J Physiol 2016 ; 594(17):4917– 31 ; AJP 2018 ; 315(3):H718–H730) and others (Am J Physiol Heart Circ Physiol. 2010 Oct ; 299(4):H1024–33.) demonstrated that suppression of angiotensin II (ANG II), with high salt diet leads to increased vascular oxidative stress due to decreased expression of antioxidative enzymes in blood vessels’ tissue. The aim of the present study was to determine the effects of HS diet on activity of antioxidative enzymes in serum. Methods: 9–11 weeks old healthy male Sprague- Dawley rats were divided in 3 groups, low salt (LS ; 0.4% NaCl for 7 days, N = 5), high salt (HS ; 4% NaCl for 7 days, N = 5) and high salt+angiotensin II group (HS+ANG II, 4% NaCl for 7 days, infused with ANG II via osmotic minipump from 4th-7th days (100 ng/kg/min/3 days), N = 6). Following dietary protocol, rats were anesthetized with ketamine (75 mg/kg) and midazolam (2.5 mg/kg) and sacrificed by decapitation. All experimental procedures were in compliance with the European Guidelines for the Care and Use of Laboratory Animals (directive 86/609) and were approved by institutional Ethical Committee. Antioxidative enzymes activity assay in serum samples was assessed by spectrophotometry. Data were analyzed by One Way Analysis of Variance test, presented as mean±SD. Statistical significance level was set to p < 0.05. Results: Serum activity (U/mgP) of catalase (LS: 0.94 ± 0.23 vs. HS: 0.50 ± 0.1, vs. HS+ANG II 0.46 ± 0.11) and superoxide dismutase (LS: 2.22 ± 0.16 vs. HS: 1.17 ± 0.25, vs. HS+ANG II: 1.04 ± 0.16) was significantly decreased in HS and HS +ANG II group compared to LS group, while glutathione peroxidase (LS: 0.17 ± 0.01) was significantly increased in HS+ANG II group (0.19 ± 0.03) compared to HS group (0.12 ± 0.04). Conclusions: High salt dietary intake decreased the activity of antioxidative enzymes, while low-dose ANG II infusion restored the activity of serum glutathione peroxidase, suggesting the physiological importance of ANG II in maintaining systemic antioxidative capacity. Acknowledgements: This work was supported by Croatian Science Foundation, Project IP-2014-09-6380.

high salt diet ; antioxidant enzymes ; angiotensin II ; Sprague-Dawley rats

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