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Published on: April 16, 2018
Urinary 5-aminolevulinic acid in lead-exposed children
Insights
Blood lead levels did not correlate with urinary 5-aminolevulinic acid (ALA) in children. However, the ALA to creatinine ratio showed a correlation, suggesting its utility as a biomarker for lead exposure effects.
Area of Science:
- Environmental Health
- Toxicology
- Biomarker Research
Background:
- Lead intoxication disrupts heme synthesis, increasing neurotoxic 5-aminolevulinic acid (ALA) levels.
- Blood lead concentration (PbB) and urinary ALA (ALAU) are biomarkers for lead exposure and effect, respectively.
- Understanding the relationship between PbB and ALAU is crucial for assessing lead's biological impact in children.
Purpose of the Study:
- To investigate the correlation between blood lead concentration (PbB) and urinary 5-aminolevulinic acid (ALAU) in lead-exposed children.
- To evaluate the utility of ALAU, adjusted for creatinine (ALAU/CR), as a biomarker of early biological effects of lead.
- To assess the impact of diurnal variation on ALAU and ALAU/CR measurements.
Main Methods:
- ALAU was measured using chemical derivatization and high-performance liquid chromatography with fluorescence detection.
- Seventy-nine children with moderate to high lead exposure were studied.
- Urine samples were analyzed for creatinine (CR) and trans,trans-muconic acid; blood was analyzed for lead (PbB).
Main Results:
- No significant correlation was found between ALAU and PbB (Spearman r=0.088, p=0.44).
- A positive correlation was observed between the ALAU/CR ratio and PbB (Spearman r=0.22, p=0.054).
- ALAU/CR ratios were consistent between morning and afternoon urine samples, supporting creatinine adjustment.
Conclusions:
- Urinary ALA concentration alone may not accurately reflect lead exposure.
- The ALAU/CR ratio shows promise as a more reliable biomarker for the early biological effects of lead in children.
- Future studies should consider ALAU/CR for validating biomarkers of lead exposure and effect in pediatric populations.
Abstract:
Lead intoxication can interfere with haem synthesis and alter the concentration of haem precursors, such as the neurotoxin 5-aminolevulinic acid, in plasma and urine. The relationship between blood lead concentration (PbB), a biomarker of lead exposure, and 5-aminolevulinic acid concentration in urine (ALAU), a biomarker of the early biological effect of lead, was examined in lead-exposed children. ALAU was assayed by chemical derivatization and high performance liquid chromatography with fluorescence detection. The study subjects were 79 children with moderate to high lead exposure recruited from a lead-poisoning prevention clinic. Their urine had been previously analysed for creatinine (CR) concentration and the benzene metabolite trans,trans- muconic acid, and their blood had been analysed for lead. We found that ALAU was not correlated with PbB (Spearman r=0.088, p=0.44), but the ratio ALAU/CR was correlated with PbB (Spearman r=0.22, p=0.054). Creatinine and ALAU concentrations were higher in urine samples collected in the afternoon than those collected in the morning, a finding that is consistent with known diurnal variation. However the ratio ALAU/CR was not different in morning and afternoon urines, supporting the use of creatinine adjustment of ALAU analysis of spot urine samples. In view of the neurotoxic properties of ALA, future validation studies of biomarkers of lead exposure and effect in children should include ALAU or ALAU/CR as potential markers of lead effect.
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