ABSTRACT
Arterial tone describes the balance between the constriction and relaxation imposed upon an artery, a dynamic state that is governed by endocrine, paracrine, and autocrine stimuli. This chapter focuses on the role of hydrogen peroxide (H2O2) as a paracrine and autocrine regulator of arterial relaxation/dilation. It describes the key features of relaxant responses to exogenous H2O2, and secondly summarizes the evidence in support of stimuli-induced formation of H2O2 as an effector molecule in arterial relaxation. Endothelial nitric oxide synthase (eNOS) is a heme- and flavin-containing enzyme that reduces oxygen and incorporates it into l-arginine to form l-citrulline and -NO. The major cellular detoxifiers of H2O2 are the cysteine peroxidases, peroxiredoxins (Prx). Glutathione Peroxidases (GPx) are selenocysteine-containing proteins that act as antioxidants by using glutathione as a cofactor to reduce H2O2 and a wide range of organic hydroperoxides to water and alcohols, respectively.
