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Hypertrophy of Cerebral Arterioles in Mice Deficient in Expression of the Gene for CuZn Superoxide Dismutase

Background and Purpose— Reactive oxygen species are believed to be an important determinant of vascular growth. We examined effects of genetic deficiency of copper-zinc superoxide dismutase (CuZnSOD; SOD1) on structure and function of cerebral arterioles. Methods— Systemic arterial pressure (SAP) and cross-sectional area of the vessel wall (CSA) and superoxide (O2–) levels (relative fluorescence of ethidium [ETH]) were examined in maximally dilated cerebral arterioles in mice with targeted disruption of one (+/−) or both (−/−) genes encoding CuZnSOD. Wild-type littermates served as controls. Vasodilator responses were tested in separate groups of mice. Results— CSA and ETH were significantly increased (P<0.05) in both CuZnSOD+/− and CuZnSOD−/− mice (CSA=435±24 and 541±48 &mgr;m2; ETH=18±1 and 34±2%) compared with wild-type mice (CSA=327±28 &mgr;m2; ETH=6%). Furthermore, the increases in CSA and ETH relative to wild-type mice were significantly greater (P<0.05) in CuZnSOD−/− mice than in CuZnSOD+/− mice (CSA=108 versus 214 &mgr;m2; ETH=12 versus 28%). In addition, dilatation of cerebral arterioles in response to acetylcholine, but not nitroprusside, was reduced by ≈25% in CuZnSOD+/− (P<0.075) and 50% in CuZnSOD−/− mice (P<0.05) compared with wild-type mice. Conclusions— Cerebral arterioles in CuZnSOD+/− and CuZnSOD−/− mice undergo marked hypertrophy. These findings provide the first direct evidence in any blood vessel that CuZnSOD normally inhibits vascular hypertrophy suggesting that CuZnSOD plays a major role in regulation of cerebral vascular growth. The findings also suggest a gene dosing effect of CuZnSOD for increases in O2–, induction of cerebral vascular hypertrophy and impaired endothelium-dependent dilatation.