Origins and function of 3-ribosylurate in bovid erythrocytes.

3-Ribosylurate is a dominant feature on high performance liquid chromatography (HPLC) profiles of acid extracts of erythrocytes from cows and buffalo, but is HPLC-undetectable in acid extracts of erythrocytes from all other species examined to date. Various aspects of this unique low molecular weight substance remain unexplored since it was first identified. In this study, the mutation(s) responsible for the appearance of ribosylurate in these cells is shown to be specific to members of both tribes of the Bovinae subfamily (Bovidae family), being detectable in the erythrocytes of both the cow and the buffalo (Bovini tribe) as well as in the kudu (Strepsicerotini tribe), but not in representative species from the other subfamilies of the Bovidae family. More specifically, expression of the mutation(s) seems to be restricted to the erythrocyte lineage of these species, ribosylurate being undetectable in cow white blood cells and primary cultures of fibroblasts. Novel evidence is presented that ribosylurate has antioxidant activity. Accumulation of high levels specifically within the haemoglobin-rich milieu of circulating erythrocytes may serve to protect perfused tissues by removing pathophysiological levels of hydrogen peroxide from plasma. Maintenance of ribosylurate levels may be important in conditions associated with oxidative stress in Bovinae.