Relationship between delta-aminolevulinic acid dehydratase genotypes and heme precursors in lead workers

BACKGROUND: The objective of this study was to investigate the relationships between genotypes of delta-aminolevulinic acid (ALA) dehydratase (ALAD) and disturbances in the heme biosynthetic pathway by lead exposure. METHODS: The subjects were 192 male lead workers and 125 control subjects. Blood lead concentrations (Pb-B), plasma ALA concentrations (ALA-P), and ALAD genotypes were determined for all subjects. In lead workers, ALAD activity, ALA in urine (ALA-U), and erythrocyte zinc protoporphyrin (ZP) were also determined. RESULTS: The frequency of ALAD2 (minor type of ALAD allele) was calculated to be 0.087 in all subjects. No significant relationship was found between ALAD2 frequency and Pb-B levels in lead workers. ALAD1 homozygotes showed significantly higher levels of ZP and ALA-P in comparison with those of ALAD2 carriers at Pb-B levels more than 20 microg/dL and 40 microg/dL, respectively. CONCLUSIONS: ALAD1 homozygotes might be more susceptible than ALAD2 carriers to disturbances in heme metabolism caused by lead exposure.