Oxidative stress: does it play a role in the genesis of essential hypertension and hypertension of uraemia?

Reactive oxygen species: general aspects Reactive oxygen species, including superoxide radicals, hydrogenperoxide, nitric oxide, peroxynitrite, hydroxyl radicals andhypochlorous acid are by-products of normal metabolic processesin cells. Reactive oxygen species can be found in several cellsincluding macrophages and vascular smooth muscle cells. At lowconcentrations reactive oxygen species can act as physiologicalmediators of cellular responses whereas higher concentrationsmay cause cell damage [1,2]. The major sources of reactive oxygenspecies are leakages from the electron transport chains of mitochondriaand endoplasmic reticulum. Cellular energy metabolism is basedon the production of ATP through the electron transport reactionin which O₂ accepts electrons and H⁺ and then is eventuallyreduced to water. Only 1–2% of the electrons are leakedto generate superoxide radicals in reactions mediated by coenzymeQ and ubiquinone and its complexes. During ageing (and probablyin patients