Nyéki A, Buclin T, Biollaz J, Decosterd L A
Group of Pharmaceutical Analysis, Section of Pharmacy, University of Lausanne, Lausanne, Switzerland.
Br J Clin Pharmacol. 2003 Jan;55(1):62-7. doi: 10.1046/j.1365-2125.2003.01730.x.
(i) To compare the phenotyping of healthy subjects for NAT2 and CYP1A2 activities with caffeine, by the simultaneous assay of the urinary metabolites AFMU and AAMU, and (ii) to ascertain whether NAT2 and CYP1A2 phenotyping is influenced by the use of AFMU or AAMU in the metabolite ratio.
Thirty-five healthy subjects (16 men, 19 women) participated to the study. Caffeine metabolite concentrations were measured in urine collected 8 h after 2.5 mg kg-1 caffeine intake using a new validated h.p.l.c. method. The metabolite ratios AFMU/1X, AFMU/(AFMU+1X+1U), AAMU/1X, AAMU/(AAMU+1X+1 U), and (AFMU+1U+1X)/17U, (AAMU+1U+1X)/17U were determined as indices of NAT2 and CYP1A2 activity, respectively.
Slow and rapid acetylators were similarly identified using the four NAT2 metabolite ratios in 139 out of 140 measurements. An appreciable amount of AAMU was present in urine that was immediately acidified and analysed. Consequently, the ratio using AFMU was lower than that using total AAMU following transformation of AFMU in basic conditions. The proportion of AFMU in urine analysed immediately expressed as AFMU/(AFMU+AAMU) ratio did not correlate with urine pH, but was a function of the acetylation phenotype, with a low intergroup variability (64 +/- 3% and 32 +/- 5%, for rapid and slow acetylators, respectively; P < 0.00001, anova). Regarding CYP1A2 activity, a good correlation (r = 0.99) was observed between the metabolite ratios calculated from AFMU and AAMU, although the ratios calculated from AFMU were proportionately and systematically lower P < 0.00001, paired t-test, slope 1.2).
This study demonstrates that both AFMU and AAMU can be used for NAT2 and CYP1A2 metabolite ratio determinations. The reported conversion of AFMU into AAMU is unlikely to explain the large amount of AAMU in urine that was acidified and analysed immediately after voiding. The results suggest that AAMU is formed not solely through a nonenzymatic hydrolysis in urine, but in vivo by a NAT2 phenotype-dependent pathway.
（i）通过同时检测尿代谢物AFMU和AAMU来比较健康受试者咖啡因代谢中NAT2和CYP1A2活性的表型，（ii）确定NAT2和CYP1A2表型是否受代谢物比率中AFMU或AAMU使用的影响。
35名健康受试者（16名男性，19名女性）参与了该研究。采用一种新的经过验证的高效液相色谱法，在摄入2.5mg/kg咖啡因8小时后收集的尿液中测量咖啡因代谢物浓度。分别测定代谢物比率AFMU/1X、AFMU/(AFMU + 1X + 1U)、AAMU/1X、AAMU/(AAMU + 1X + 1U)以及(AFMU + 1U + 1X)/17U、(AAMU + 1U + 1X)/17U作为NAT2和CYP1A2活性指标。
在140次测量中的139次中，使用四种NAT2代谢物比率同样能鉴别出慢乙酰化者和快乙酰化者。在立即酸化并分析的尿液中存在相当数量的AAMU。因此，在碱性条件下AFMU转化后，使用AFMU的比率低于使用总AAMU的比率。立即分析的尿液中AFMU以AFMU/(AFMU + AAMU)比率表示，与尿液pH值无关，但与乙酰化表型有关，组间变异性较低（快乙酰化者和慢乙酰化者分别为64±3%和32±5%；P<0.00001，方差分析）。关于CYP1A2活性，尽管由AFMU计算出的比率成比例且系统性地较低（P < 0.00001，配对t检验，斜率1.2），但观察到由AFMU和AAMU计算出的代谢物比率之间有良好的相关性（r = 0.99）。
本研究表明AFMU和AAMU均可用于NAT2和CYP1A2代谢物比率的测定。所报道的AFMU向AAMU的转化不太可能解释排尿后立即酸化并分析的尿液中大量的AAMU。结果表明AAMU不仅通过尿液中的非酶水解形成，而且在体内通过NAT2表型依赖性途径形成。
