INTERNAL MAMMARY ARTERY GRAFTS REACTIVITY IN HYPERTENSIVE PATIENTS. ROLE OF STRETCHING IN EXTRAENDOTHELIAL NITRIC OXIDE

JOO TURONI C. COVIELLO A.; PERAL DE BRUNO M; MUNTANER J.; PROTO V

CLINICAL AND EXPERIMENTAL HYPERTENSION

EDITORIAL MARCEL DEKKER Inc

Lugar: USA; Año: 2007 vol. 29 p. 327 - 344

1064-1963

Abstract Background: Internal mammary artery (IMA) used in bypass coronary surgery remains patent for a longer time that other grafts like saphenous veins; however, its biological characteristics remain incompletely defined. Objective: To compare, in IMA grafts from hypertensive (HT) and normotensive (NT) patients: 1) the presence of endothelium and their functionability, 2) the response to passive stretching and basal tone 3) the reactivity to exogenous vasoconstrictors 4) the role of stretching in NO-release and 5) the possible extraendothelial NO source. Methods and Results: IMA rings contractility, presence of endothelium and nitrite release were studied. An endothelial dysfunction associated with hypertension was found. IMA rings from HT had an impaired response to passive stretching resulting in a decreased relaxation. All IMA grafts had an increased basal tone demonstrated by relaxation to SNP, however a lesser response was found in HT. Interestingly, It was demonstrated that NO release was present in IMA grafts, despite an endothelial dysfunction and that stretching increased NO release. This effect was inhibited by Ca2+-free media, L-NAME and a specific neuronal NO synthase (nNOS) inhibitor. Furthermore, demonstration of nNOS presence in smooth muscle cells by immunohistochemistry supports a role of extraendothelial NO. Conclusion: We demonstrate the impact of hypertension in IMA grafts producing: 1) increased endothelial dysfunction, 2) reduced response to passive stretching 3) increased basal tone and 4) impaired responsiveness to exogenous vasoconstrictors and NO release. A specific role of stretching in extraendothelial NO release was demonstrated, which may have an important role in the outcome of IMA grafts due to the protective actions of NO, even in absence of endothelium. Keywords: IMA grafts, hypertension, endothelial dysfunction, vascular reactivity, extra endothelial nitric oxide synthase