Myocardial release of hypoxanthine and urate during angioplasty

Abstract

Oxygen free radicals have been implicated in ageing, oncogenesis and atherogenesis [1], One potential source is xanthine oxidase, the oxyradical-producing form of xanthine oxidoreductase. This enzyme catabolizes the high-energy-phosphate metabolites hypoxanthine and xanthine to urate (Fig. 1). Ischemia converts the native form of the enzyme, xanthine reductase, to xanthine oxidase [2]. During reperfusion oxygen is available for the production of superoxide and hydroxyl radicals [3, 4], both of which are strongly suspected to cause tissue damage [3, 5–7]. Xanthine oxidoreductase activity is present in the myocardium of a number of species [8], but its presence in human heart is controversial. In autopsy material several authors measured high xanthine oxidoreductase activity [9, 10]. Using histochemical techniques, Jarasch and coworkers found large amounts of the enzyme in human heart endothelium [11]. On the other hand, several authors reported very low to undetectable xanthine oxidoreductase activity in human heart [12–14]. We present evidence that the heart of (a number of) cardiac patients produces significant amounts of urate. Thus xanthine oxidoreductase may be active in the human heart in vivo.