Zinc supplementation improves heme biosynthesis in rats exposed to lead

BACKGROUND Lead acetate (Pb) inhibits heme biosynthesis through inhibition of delta-aminolevulinic acid dehydrogenase (delta-ALAD), copro porphyrinogen oxidase, and ferro chelatase. Zinc supplementation increases lead-binding metallothionein proteins. The purpose of this study was to find evidence that zinc supplementation prior to lead exposure improves heme biosynthesis in rats. METHODS This was a randomized post-test only control-group design study involving 28 rats assigned to 4 groups (1 control and 3 treatment groups). The treatment groups were supplemented with zinc at doses of 0.2, 0.4, and 0.8 mg daily by gavage for 3 weeks. From week 4 to 13, all groups were exposed to lead 0.5 g/kg BW/day by gavage. At the end of week 13, delta-ALAD, erythrocyte protoporphyrin (EPP), and heme concentrations were determined by means of ELISA. One-way ANOVA, followed by Bonferroni's test was used to analyse the data. RESULTS Mean d-ALAD concentrations decreased from the control group down to treatment group 3 (0.24 +/- 0.20; 0.15 +/- 0.15; 0.12 +/- 0.11; 0.05 +/- 0.06 ng/mean per unit). Mean EPP concentrations decreased from the control group down to treatment group 3 (1.96 +/- 0.50; 1.24 +/- 0.24; 1.03 +/- 0.05; 0.62 +/- 0.16 ng/mL). Mean heme concentrations increased from the control group up to treatment group 3 (8.07 +/- 2.64; 10.11 +/- 2.27; 10.04 +/- 1.65; 11.41 +/- 2.58 mu M). ANOVA followed by Bonferroni showed that EPP concentrations differed significantly between the control group and treatment group 3 (p=0.00). CONCLUSION Zinc supplementation prior to lead exposure improves heme biosynthesis in rats exposed to lead.