Superoxide Excess in Hypertension and Aging

Abstract
There is evidence in humans that hypertension and aging similarly impair endothelial function, although the mechanism remains unclear. Superoxide anion (O2−) is a major determinant of nitric oxide (NO) bioavailability and thus endothelial function. We sought to determine the relationship between endothelial function, O2−, and age in normotensive Wistar-Kyoto (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP). Aortic rings were removed from female WKY and SHRSP at 3 to 4 months (young) and 9 to 12 months (old). O2− generation by aortic rings was measured before and after removal of the endothelium or incubation with NG nitro-l-arginine methyl ester, diphenyleneiodonium, or apocynin. Levels of p22phox were studied with immunohistochemistry and used as a marker of NAD(P)H oxidase expression. NO bioavailability was significantly lower in old WKY compared with young WKY (P=0.0009) and in old SHRSP compared with young SHRSP (P=0.005). O2− generation was significantly greater in old WKY compared with...

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