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

Abstract

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 microg/dL and its impact on selected oxidative stress parameters and delta-aminolevulinic acid dehydratase (delta-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, delta-ALAD, malondialdehyde (MDA) and glutathione (GSH) in blood and catalase (CAT) in RBCs. Mean level of blood lead was 9.96 +/- 3.63 microg/dL (4.62-18.64); 43% of adolescents crossed the Centre for Disease Control (CDC) intervention level of 10 pg/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 microg/dL (7.40 +/- 1.62) and >10 microg/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, delta-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 6-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, delta-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 6-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.