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Updated: Aug 13, 2026
Measurement of Heme Synthesis Levels in Mammalian Cells
Published on: July 9, 2015
Indicators of internal dose of lead in relation to derangement in heme synthesis
Insights
Blood lead (Pb-B) levels may not reliably indicate internal lead dose in children. Chelatable lead and erythrocyte protoporphyrin (EP) are better indicators of lead
Area of Science:
- Environmental Health
- Toxicology
- Biochemistry
Background:
- Lead exposure is a significant public health concern, particularly in children.
- Assessing internal lead dose and its biological effects is crucial for effective clinical management.
- Traditional biomarkers like blood lead (Pb-B) may have limitations in accurately reflecting lead's impact.
Purpose of the Study:
- To evaluate the reliability of various biomarkers for assessing lead absorption and its biological effects.
- To compare the effectiveness of blood lead (Pb-B), urine lead (Pb-U), chelatable lead, and erythrocyte protoporphyrin (EP) in asymptomatic children.
- To identify optimal biomarkers for monitoring lead exposure and its impact on heme synthesis.
Main Methods:
- Simultaneous measurements of Pb-B, Pb-U, chelatable lead, ALA-U, and EP in asymptomatic children with increased lead absorption.
- Development of a simple AAS method for measuring chelatable lead in urine.
- Description of a new wet digestion technique compatible with ASV.
Main Results:
- Linear dose-effect relationships were observed between Pb-U and chelatable lead (dose indicators) and ALA-U and EP (effect indicators).
- Pb-B was found to be an unreliable indicator of internal lead dose within a specific range (48-68 µg Pb).
- EP demonstrated a stronger correlation with chelatable lead than Pb-B, suggesting its utility in predicting soft tissue lead concentration.
Conclusions:
- Relying solely on Pb-B for clinical management of lead exposure may be insufficient, especially for high-risk groups.
- Chelatable lead appears to be the most accurate biomarker for reflecting lead's inhibitory effect on heme synthesis and soft tissue lead concentration.
- Micro tests for EP, particularly the zinc protoporphyrin fraction, are valuable tools for monitoring long-term trends in soft tissue lead levels.
Abstract:
Simultaneous measurements of Pb-B, Pb-U, chelatable lead, ALA-U and EP have been made in a group a asymptomatic children with increased lead absorption. Although the group is small, the results are internally consistent and show linear dose-effect relationships between Pb-U and chelatable lead (indicators of dose) and ALA-U and EP (indicators of lead's effect on heme synthesis). The data show, however, that Pb-B in a rather narrow range (48-68 mug Pb) is not a reliable indicator of the internal dose of lead. These results, as well as others, raise questions concerning the validity of relying exclusively on Pb-B in the clinical management of groups such as young children in old houses and lead-exposed workmen who are at increased risk for plumbism; The results suggest that chelatable lead is most closely related to lead's inhibitory effect on heme synthesis and that, biologically, it may serve as the best "chemical biopsy" of soft tissue lead concentration; A simple AAS method for measureing chelatable lead in urine is described; A new wet digestion technique which is compatible with ASV is also described. EP is apparently a better predictor of chelatable lead than Pb-B. Micro tests for EP, especially the zinc protoporphyrin fraction, are simple and highly useful in monitoring long-term trends in soft tissue levels in individual patients.
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