Distribution of xanthine oxidase activity in a Nigerian population

Xanthine oxidase (XO) is one of the two interconvertible forms of xanthine oxidoreductase and well-studied for its role in purine catabolism and that of other purine analogues, drugs especially. Our study investigated the incidence of polymorphism in phenotypes along with the influence of gender and age on enzyme activity in a Nigerian population. Caffeine (110 mg) was administered to each of 129 healthy, unrelated subjects who were nonsmokers. Urine voided within 7 h after dosing was collected for a high-performance liquid chromatographic analysis of metabolites, and the urinary molar ratio of metabolites was used as marker for enzyme activity. Statistical analysis of data was carried out to identify the prevalent phenotypes and also assessed the influence of age and sex on enzyme activity. A sevenfold variation in XO activity with a population mean (+/- SD) molar ratio of 0.43 +/- 0.15 and median (interquartile range) of 0.42 (0.16) was observed. Distinctly higher enzyme activity was also recorded in 8 % of the study population, and there was no correlation (P > 0.05) between enzyme activity and the studied covariates. Our study confirmed the existence of polymorphism in xanthine oxidase activity in Nigerians and also the incidence of individuals with distinctly higher XO activity in the population.