Increased xanthine oxidase activity in idiopathic pulmonary arterial hypertension.

Oxidative stress may play a role in the pathogenesis of idiopathic pulmonary arterial hypertension (IPAH) [1–4]. A major contributor to oxidative stress is the endothelium-bound enzyme xanthine oxidase (XO), which is involved in the generation of superoxide anions and peroxynitrite [5]. These reactive oxygen species have been implicated in endothelial dysfunction and vascular damage [5]. In vivo, XO is bound to the surface of endothelial cells by glycosaminoglycans and can be released into plasma by heparin bolus injection [6]. XO activity has not been assessed in patients with IPAH, but increased activity of this enzyme is suggested by hyperuricaemia, a common finding in patients with IPAH [7].