URINARY 5-AMINOLEVULINIC ACID (ALA) ADJUSTED BY CREATININE - A SURROGATE FOR PLASMA ALA

5-Aminolevulinic acid (ALA) is the first intermediate substrate in the heme synthetic pathway and is the substrate of aminolevulinic acid de hydratase (ALAD, porphobilinogen synthase). Because lead effectively i nhibits ALAD activity, resulting in accumulation of ALA in urine and b lood, urinary ALA (ALAU) has been used as a biomarker for lead exposur e or early biologic effect of lead. Intraindividual variation in urina ry excretion of ALA requires the use of 24-hour urine samples or adjus tment of single urine samples by other normalizing variables, such as urinary creatinine concentration. Previous studies of ALA U concentrat ion have used various adjustment methods; however, few have compared c reatinine-adjusted ALAU concentration with ALA concentration in plasma (ALAP) from subjects with low (<30 mu g/dL) to moderate (< 60 mu g/dL ) levels of blood lead. To determine if creatinine adjusted ALA U is a ssociated with ALAP, we measured ALA U, ALAP, and urinary creatinine i n 65 Korean lead workers with blood lead concentrations in the range o f 14-60 mu g/dL. ALA U, ALA U/creatinine, or ALA U/log creatinine all correlated with ALAP, However, ALAU/creatinine correlated more closely with ALAP based on Spearman's r (r(s) 0.40, P = 0.0009), supporting t he use of ALA/creatinine in single urine samples as a surrogate for AL AP.