Grant D M, Tang B K, Campbell M E, Kalow W
Br J Clin Pharmacol. 1986 Apr;21(4):454-8. doi: 10.1111/j.1365-2125.1986.tb05222.x.
Caffeine (5 mg kg-1) was administered orally to two healthy, non-smoking subjects on three separate occasions--before, and during therapy with the xanthine oxidase inhibitor allopurinol at doses of either 300 or 600 mg daily. Plasma and urinary levels of methylxanthines, endogenous oxypurines and allopurinol and its metabolite oxypurinol were measured using h.p.l.c. analyses. Allopurinol treatment caused a specific, dose-dependent inhibition of the conversion of the caffeine metabolite 1-methylxanthine (1X) to 1-methyluric acid (1U). A good correlation was observed in both subjects between the urinary 1U/1X molar ratio and the ratio of endogenous urate to hypoxanthine + xanthine at the different allopurinol doses, supporting the proposal that the 1U/1X molar ratio after caffeine intake provides an in vivo index of xanthine oxidase activity in man.
在三个不同时间段，对两名健康、不吸烟的受试者口服给予咖啡因（5毫克/千克）——一次是在治疗前，另外两次是在使用黄嘌呤氧化酶抑制剂别嘌呤醇治疗期间，别嘌呤醇的剂量分别为每日300毫克或600毫克。使用高效液相色谱分析法测定血浆和尿液中甲基黄嘌呤、内源性氧嘌呤、别嘌呤醇及其代谢产物氧嘌呤醇的水平。别嘌呤醇治疗导致咖啡因代谢产物1-甲基黄嘌呤（1X）向1-甲基尿酸（1U）的转化受到特异性的、剂量依赖性抑制。在不同别嘌呤醇剂量下，两名受试者的尿1U/1X摩尔比与内源性尿酸与次黄嘌呤+黄嘌呤的比值之间均观察到良好的相关性，这支持了以下观点：摄入咖啡因后的1U/1X摩尔比可作为人体黄嘌呤氧化酶活性的体内指标。
