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Superoxide Scavenging in vivo Increases Endothelial Nitric Oxide Bioavailability in Sprague- Dawley Rats on a High Salt Diet

Introduction: Previously, we showed that superoxide scavenger TEMPOL in vitro increased the flow-induced dilatation (FID) of middle cerebral arteries (MCA) in rats on high salt (HS) diet which was NO- dependent response. Present study aimed to determine the effect of HS diet on flow-induced endothelial NO production. Method: Eleven weeks old male Sprague-Dawley rats were divided in 3 groups(N=5 per group): low salt(LS) group, HS(4%NaCl) and HS+TEMPOL(4%NaCl+TEMPOL 1 mM/L in drinking water ad libidum) for 7 days. Following diet protocol, rats were anesthetized with ketamine (75mg/kg) and midazolam (2.5mg/kg) and decapitated. MCA were isolated and cannulated on pressure myograph with or without flow (at ∆80 mmHg), in the absence/presence of the NOS inhibitor L-NAME. NO production was determined by DAF- 2DA to DAF-2T conversion fluorescence assay. All experimental procedures conformed to the European Guidelines for the Care and Use of Laboratory Animals (directive 86/609) and were approved by institutional Ethical Committee.Data are presented as Fluorescence Intensity (AU), average±SEM, p<0.05 was significant. Results: Basal NO production in no-flow condition was similar among groups. L-NAME blocked the production of NO in each group ((LS:35.4±3.17 vs. LS+L-NAME:22.8±3.58 ; HS:32.4±6.48 vs. HS+L-NAME:14.2±1.15 ; HS+TEMPOL:35.4±4.29 vs. HS+TEMPOL+L- NAME:19.2±2.35, p<0.05).Flow-induced NO production was significantly lower in HS group (21.31±0.61) compared to flow-induced NO production in LS (31.26±3.22, p=0.016) and HS+TEMPOL group(31.94±2.11, p=0.001) L-NAME blocked flow-induced NO production similarly among groups (flow:LS 31.26±3.22 vs. LS+L-NAME:18.08±1.66 ; HS:21.31±0.61 vs. HS+L-NAME:17.46±1.25 ; HS+TEMPOL:31.94±2.11 vs. HS+TEMPOL+L-NAME:18.45±0.95, p>0.05). Conclusions: Present study determined that HS diet suppresses the flow-induced NO production in MCA. Superoxide scavanging restores flow-induced NO production and bioavailability in HS+TEMPOL group.Funding: HRZZ#IP-2014-09-6380 (V-ELI Athero).

high salt diet, oxidative stress, superoxide, Sprague-Dawley rats

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