Sithisarankul P, Schwartz B S, Lee B K, Strickland P T
Department of Environmental Health Sciences, Johns Hopkins School of Hygiene and Public Health, Baltimore, Md. 21205, USA.
J Occup Environ Med. 1998 Oct;40(10):901-6. doi: 10.1097/00043764-199810000-00011.
5-Aminolevulinic acid (ALA) is the first intermediate substrate in the heme synthetic pathway and is the substrate of aminolevulinic acid dehydratase (ALAD, porphobilinogen synthase). Because lead effectively inhibits ALAD activity, resulting in accumulation of ALA in urine and blood, urinary ALA (ALAU) has been used as a biomarker for lead exposure or early biologic effect of lead. Intraindividual variation in urinary excretion of ALA requires the use of 24-hour urine samples or adjustment of single urine samples by other normalizing variables, such as urinary creatinine concentration. Previous studies of ALAU concentration have used various adjustment methods; however, few have compared creatinine-adjusted ALAU concentration with ALA concentration in plasma (ALAP) from subjects with low (< 30 micrograms/dL) to moderate (< 60 micrograms/dL) levels of blood lead. To determine if creatinine-adjusted ALAU is associated with ALAP, we measured ALAU, ALAP, and urinary creatinine in 65 Korean lead workers with blood lead concentrations in the range of 14-60 micrograms/dL. ALAU, ALAU/creatinine, or ALAU/log creatinine all correlated with ALAP. However, ALAU/creatinine correlated more closely with ALAP based on Spearman's r (rs = 0.40, P, = 0.0009), supporting the use of ALA/creatinine in single urine samples as a surrogate for ALAP.
5-氨基乙酰丙酸（ALA）是血红素合成途径中的首个中间底物，也是氨基乙酰丙酸脱水酶（ALAD，卟胆原合酶）的底物。由于铅能有效抑制ALAD活性，导致ALA在尿液和血液中蓄积，尿ALA（ALAU）已被用作铅暴露或铅早期生物学效应的生物标志物。ALA尿排泄的个体内差异需要使用24小时尿液样本，或通过其他标准化变量（如尿肌酐浓度）对单次尿液样本进行校正。以往关于ALAU浓度的研究采用了各种校正方法；然而，很少有研究将肌酐校正后的ALAU浓度与血铅水平低（<30微克/分升）至中度（<60微克/分升）的受试者血浆中的ALA浓度（ALAP）进行比较。为了确定肌酐校正后的ALAU是否与ALAP相关，我们测量了65名血铅浓度在14 - 60微克/分升范围内的韩国铅作业工人的ALAU、ALAP和尿肌酐。ALAU、ALAU/肌酐或ALAU/log肌酐均与ALAP相关。然而，基于Spearman相关系数r（rs = 0.40，P = 0.0009），ALAU/肌酐与ALAP的相关性更强，这支持将单次尿液样本中的ALA/肌酐用作ALAP的替代指标。
