[Nitric oxide synthases and peripheral cardiovascular system]

The synthesis of nitric oxide (NO) is catalysed by nitric oxide synthases which exist in at least three distinct isoforms. These enzymes catalyse the oxidation of the amino acid L-arginine to give rise to L-citrulline and NO. The different cell types comprising cardiac muscle express one or more of the three isoforms (neuronal, inductible, endothelial) of NO synthases. Recently, a mitochondrial nitric oxide synthase has been isolated. A complexity of NO synthase exists with distinct domains and multitude of cofactors. NO synthases are able to produce not only NO but also superoxide O2-. (uncoupled reaction). These two products can react together extremely rapidly to form the potent oxidant peroxynitrite. The formation of peroxynitrite has been implicated in the pathology of a large number of conditions involving oxidative stress such as atherosclerosis and heart failure.