Delta-aminolevulinic acid dehydratase inhibition and oxidative stress in relation to blood lead among urban adolescents

To explore lead-induced oxidative stress among urban adolescents, the present study, the first from India, was designed to determine the proportion of urban adolescents with blood lead > 10 μg/dL and its impact on selected oxidative stress parameters and delta-aminolevulinic acid dehydratase (δ-ALAD) inhibition, which could be used as biomarkers of lead intoxication. A total of 39, urban, male adolescents, drawn from Lucknow and adjoining areas, were recruited to determine lead, d-ALAD, malondialdehyde (MDA) and glutathione (GSH) in blood and catalase (CAT) in RBCs. Mean level of blood lead was 9.96 ± 3.63 μg/dL (4.62 - 18.64); 43% of adolescents crossed the Centre for Disease Control (CDC) intervention level of 10 mg/dL blood lead. On the basis of blood lead levels (BLLs), adolescents were categorized into two groups: Group I and Group II had a blood lead < 10 μg/dL (7.40 ± 1.62) and < 10 μg/dL (13.27 ± 2.67), respectively, with significantly different mean values (P < 0.001). Age, sex, body mass index (BMI), Hb level (malnutrition), and area of living as confounders of lead exposure and toxicity were not statistically different between the two groups. However, d-ALAD activity was significantly lower (P < 0.001), while CAT activity was higher in Group II than in Group I (P < 0.01). MDA level was also significantly higher in Group II compared to Group I (P < 0.001). There were significant negative correlation of BLL with d-ALAD (r = -0.592, P < 0.001), and positive correlations with CAT (r= -0.485, P < 0.01) and MDA (r = -0.717, P < 0.001). Interestingly, d-ALAD, in turn, had significant negative correlations with CAT (r = -0.456, P <0.01) and MDA (r = -0.507, P < 0.01). Results of the present pilot study provide clues to the possible low level of lead-induced oxidative stress in urban adolescents, suggesting that lead-induced d-ALAD inhibition can also be an indicator of oxidative stress. The potential of oxidative stress parameters to be used as biomarkers of lead toxicity warranted further investigation.