Our understanding of this enzyme has changed dramatically in the past few years. Firstly, it is now known that the conversion of purines to uric acid is only one of the functions of this redox centres enzyme. There are two other redox centres in the enzyme, one site, which is known to reduce oxygen to superoxide and a other site - an iron sulphur centre whose function is less clear. Recent studies have shown that the enzyme can serially reduce nitrates to nitrites, nitrites to nitric oxide and nitric oxide reacts with superoxide very rapidly to produce peroxynitrite. Nitric oxide, superoxide and peroxynitrite are powerful anti-bacterial systems. This raises the question -does the joint have a powerful anti-bacterial system and is the development of gout a reflection of this process?
Our interest in this area was stimulated when we took note of the fact that the levels of xanthineoxidase were very high in breast milk of lactating mammals (Stevens C.R. et al., 2000). A series of studies have now clearly demonstrated that the function of this enzyme is antibacterial and its purpose to protect the neonatal stomach and perhaps the lactating breast.
Now we shall consider infective and reactive arthropathies. Isolating intact organisms from the joint of patients with a bacteriamia and septicaemia is very difficult and indeed, most bacteraemic and septicaemic illnesses are not associated with an infective arthritis. The synovial membrane - is a fragile structure with multiple vessels for the most part supported by fatty tissue, potentially easily traumatised and able to leak. This structure is necessary for the correct physiological function of the joint allowing cartilage, which is avascular, but metabolic active. It is therefore at risk, and the presence of an antibacterial system, especially for the joint, would minimise this.
The evidence is recently found that the synovial micro vessels have an enhanced capacity to generate reactive nitrogen species and preliminary evidence that isolated synovial endothelial cells have an enhanced capacity prepared with other micro vessels to produce xanthineoxidase. It allows to connect these observations, and suitable experiments to do conclusion. In this presentation, we use teleological centred arguments to develop this hypothesis utilizing examples from other species in the animal kingdom.The article is admitted to the International Scientific Conference "Present-day problems of experimental and clinical medicine", Thailand (Phuket), 19-27th December, 2007, came to the editorial office on 09.11.07.