The activity of xanthine oxidase in heart of pigs, guinea pigs, rabbits, rats, and humans.

We isolated and purified xanthine oxidase by Sephadex gel filtration and assayed the activity of the enzyme by urate production which we measured by HPLC and UV absorption at 290 nm. We applied this method to extracts of liver and heart of rats, guinea pigs, rabbits, and pigs and to heart of dogs and humans. We found that pig hearts do not exhibit xanthine oxidase activity and that human and rabbit hearts produced small amounts of urate only after hours of incubation. We conclude that xanthine oxidase does probably not play an important part in the mechanisms leading to myocardial infarction using the free radical generating pathway, because it is absent in one species (pig) and barely detectable in two others (rabbit and man) that are known for their rapid and complete infarction following acute coronary occlusion.