engleski

Tempol in vivo restores impaired relaxation of middle cerebral arteries in Sprague-Dawley rats on high salt diet

Objective: It is known that increased dietary NaCl intake leads to increased vascular oxidative stress, related to impaired vascular responses to various stimuli. Our previous studies have shown that high salt (HS) intake reduces vascular responses to flow-induced dilation (FID) of middle cerebral artery (MCA) in Sprague-Dawley (SD) rats, and in vitro application of TEMPOL restores FID while it had no effect in rats on low salt (LS) diet (1). The aim of the present study was to determine the effect of simultaneous TEMPOL in vivo consumption with HS diet on MCA responses to FID in SD rats. Design and method: 11-weeks old healthy male SD rats were divided in 4 groups: low salt group (LS) fed with standard rat chow (0.4% NaCl, N=16) ; LS+TEMPOL (0.4% NaCl+1mM ; dissolved in tap water, N=10) ; high salt group (HS) (4%NaCl, N=15) ; HS+TEMPOL (4% NaCl+TEMPOL (1mM ; dissolved in tap water), N=16) for 7 days. Prior to decapitation, rats were anesthetized with 75 mg/kg ketamine+2.5 mg/kg midazolam. MCA were isolated and cannulated (DMT pressure myograph) for vascular reactivity measurements in response to stepwise increase in pressure gradient (Δ10-Δ100), in the absence/presence of the NOS inhibitor L-NAME, COX-1, 2 inhibitor indomethacin (INDO) and selective inhibitor of microsomal CYP450 epoxidase activity MS-PPOH. To test differences among groups Two-way ANOVA was used, p<0.05 considered significant. All experimental procedures conformed to the European Guidelines for the Care and Use of Laboratory Animals (directive 86/609) and were approved by the local and national Ethical Committee (Class: 602-04/14-08/06, No 2158-61-07-14-04). Results: FID was reduced in HS group at Δ40, Δ60 and Δ100 compared to LS group, at Δ20, Δ40 and Δ60 compared with HS+TEMPOL group, and at Δ10, Δ40 and Δ60 compared to LS+TEMPOL group (p<0.05). L-NAME, INDO and MS-PPOH reduced FID in LS and LS+TEMPOL compared with baseline, independently and in combination. In HS group only L-NAME statisticaly reduced FID at Δ20- Δ60 pressure gradient. In HS+- TEMPOL group FID was reduced in the presence of L- NAME and MS-PPOH at Δ20- Δ100 pressure gradient, independently and in combination (p<0.05). Conclusions: These results demonstrate that high salt intake impaires vascular responses to FID and SOD mimetic TEMPOL in vivo restores FID by reducing the level of vascular oxidative stress. In LS group NO, COX-1, 2 metabolites and EETs could contribute to mechanism of FID. While NO mediates FID in both HS and HS+TEMPOL groups, EETs could also contribute to FID in HS+TEMPOL rats, suggeting that change in oxidative stress levels (due to HS or TEMPOL intake) may affect the metabolism of arachidonic acid shifting the production of metabolites among the pathways. Cosic A, Jukic I, Stupin A, Mihalj M, Mihaljevic Z, Novak S, Vukovic R, Drenjancevic I. Attenuated flow- induced dilation of middle cerebral arteries is related to increased vascular oxidative stress in rats on a short- term high salt diet.J Physiol. 2016 Apr 8. doi: 10.1113/JP272297. [Epub ahead of print] Acknowledgement:This work has been supported by Croatian Science Foundation under the project # IP- 2014-09-6380 Where applicable, the authors confirm that the experiments described here conform with the Physiological Society ethical requirements.

high salt diet ; middle cerebral arteries ; oxidative stress ; tempol

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