The HPLC conditions for separating and detecting uric acid are described above. == VIII. decreased effectiveness of XOR inhibitors in controlling severe whole-brain ischemia in a mouse model was the low levels of expression of XOR in the mouse brain. Keywords: whole-brain ischemia, xanthine Histone Acetyltransferase Inhibitor II oxidoreductase, three-vessel occlusion model, allopurinol, febuxostat == Introduction == Resuscitation from global cerebral ischemia that is associated with cardiac arrest often results in poor neurological outcomes. 1, 2)Postcardiac arrest treatment is important to minimize brain injury3); however , even with good treatment, outcomes need to be improved. Further development of treatments is necessary for patients with poor neurological prognoses. Several rat models of global cerebral ischemia have been established. 46)However, taking into consideration the use of Histone Acetyltransferase Inhibitor II gene-modified animals, there is merit to developing a mouse model, and some models have Histone Acetyltransferase Inhibitor II been reported. Yonekura et al. have presented a three-vessel occlusion model involving temporary occlusion of the basilar artery with a miniature clip. 7)This model is reproducible; however , the technique is extremely challenging. In contrast, Thal et al. have reported a two-step approach for disconnecting cerebral circulation from the vertebral collateral blood flow by coagulating the basilar artery. 8)These models are useful for studying events, such as cardiopulmonary arrest states, that involve whole-brain ischemia. Some enzymes are activated during global and focal cerebral ischemia and reperfusion (I/R), leading to the production of excessive reactive oxygen species (ROS). 911)Among them, xanthine oxidoreductase (XOR) is one of the best studied ROS-generating enzymes. 12)This enzyme catalyzes the oxidation of hypoxanthine to xanthine and xanthine to uric acid with the concomitant reduction of NAD+or molecular oxygen. Mammalian XOR exists as xanthine dehydrogenase (XDH), which prefers NAD+as an electron donor. However , XDH is converted to xanthine oxidase (XO) in some situations, and XO prefers O2. 13)McCord has proposed that the conversion of XDH to XO during tissue reperfusion Histone Acetyltransferase Inhibitor II is the basis of the I/R mechanism. 12)Several experimental and clinical studies have been conducted on cerebral ischemia in order to study the role of XOR and the protective effects of XOR inhibitors, such as allopurinol (GlaxoSmithKline Pharma Ltd., Research Triangle Park, North Carolina, USA). 14)Recently, some XOR tight-binding inhibitors have been developed for anti-gout drug. Febuxostat (Teijin Pharma Ltd., Tokyo) is a novel potent XOR inhibitor15)and that was recently approved by the Food and Drug Administration for clinical use. Here, we adopted a three-vessel occlusion mouse model as a global severe MSK1 cerebral I/R model and analyzed the effects of allopurinol and febuxostat in the model. == Materials and Methods == == I. Animals and materials == Six- to nine-week-old male C57BL/6 mice (CLEA Japan Inc., Tokyo), weighing 1922 g, were allowed free access to food and water before the experiments. All experimental procedures in this study were Histone Acetyltransferase Inhibitor II approved by the institutional animal care committee of Nippon Medical School. Extreme care was taken throughout the study to minimize the pain and discomfort to the animals. Febuxostat, 2-[3-cyano-4-(2-methylpropoxy) phenyl]-4-methyl-5-thiazolecarboxylic acid, was obtained from Carbosynth Ltd. (Berkshire, UK). Allopurinol [4-hydroxypyrazolo(3, 4-d)pyrimidine] and oxypurinol [4, 6-dihydroxypyrazolo(3, 4-d) pyrimidine] were obtained from Sigma-Aldrich Co. LLC (St. Louis, Missouri, USA). All other chemicals and reagents were of reagent grade or equivalent and were purchased from Wako Pure Chemical Industries, Ltd., Osaka. == II. Determination of plasma XOR inhibitor concentrations == Blood samples were collected with heparinized syringes from the descending aorta.