OXIDATIVE STRESS IN HYPERTENSIVE PATIENTS INDUCES AN INCREASED CONTRACTILITY IN VEIN GRAFTS INDEPENDENT OF ENDOTHELIAL FUNCTION

JOO TURONI CLAUDIO ; MARAÑÓN RODRIGO ; KARBINER MARIA; MUNTANER JUAN ; PROTO VÍCTOR ; PERAL DE BRUNO MARÍA

International Journal of Hypertension

Hindawi Publishing Corporation

Año: 2011

2090-0392

BACKGROUND: Saphenous veins (SV) are currently used in coronary artery bypass grafting surgery; however, these vessels present an impaired patency. Objective: To evaluate the impact of oxidative stress on vascular reactivity to vasoconstrictors and on nitric oxide (NO) bioavailability in SV with endothelial dysfunction from hypertensive patients (HT). METHODS: Endothelial function, vascular reactivity, oxidative state, nitrites and NO release were studied in isolated SV rings from HT and normotensive patients (NT). Endothelial function was assayed in vitro by acetylcholine response and by immunohistochemistry. Only rings with endothelial dysfunction were used. RESULTS: In HT, a hyperreactivity to angiotesin II and noradrenaline was found. This hyperreactivity was reverted by diphenylene iodonium (DPI). In NT, no effect of DPI was obtained. Incubation with Nw-nitro-L-arginine methyl ester (L-NAME) increased the contractile response only in NT. NO was present in SV, even in the absence of endothelial function. Nitrites were higher in NT than in HT (1066.1±86.3 pmol/mg;n=11 vs. 487.8±51.6;n=23; p<0.01). Nitrite contents were inhibited by L-NAME and S-methyl-L-thiocitrulline (nNOS inhibitor) in both HT and NT. L-arginine reversed these effects. Tempol and DPI increased nitrites and NO contents only in HT. The anti-nNOS-stained area by immunohistochemistry was higher in NT than HT. HT showed an elevation of protein carbonyl contents, conjugated diene, oxidized/reduced glutathione ratio and thiobarbituric acid reactive substances. CONCLUSIONS: Extraendothelial NO counter-regulates contractility in SV. However, this action could be altered in hypertensive situations by an increased oxidative stress or a decreased ability of nNOS to produce NO. Further studies should be performed to evaluate the implication of these results in graft patency rates.